Buying or building a computer used to be a little simpler, since the goal was to get a machine with as much power as you could afford. Nowadays most CPUs are exceptionally fast, and even a low-end processor will still net you a pretty fast machine. Instead, the more important choices you need to make have more to do with every other component.

We're going to go over every major component, as it applies to desktops and laptops that you buy or build, to help you figure out your best options for your computing needs. Each section will have a description and an option of LOW END (ultraportables, netbooks, and cheap desktops), MIDDLE OF THE ROAD (average to pretty damn good laptops and desktops), and HIGH PERFORMANCE (gaming rigs, media workstations, and any super-fast computers). Based on your needs, chose the most applicable category in each section (keep track of which you're choosing most) and we'll suggest what machine will likely fit your needs at the end.

The Components

Case/Enclosure

The case/enclosure you choose for your computer can mean a number of things, but the important consideration here is size. If you're building or buying a desktop, you have to decide whether or not you want a big or small machine. If you're buying a laptop (because it's unlikely you're building one), you have to choose between a variety of sizes (e.g.: a bulky "desktop replacement," a regular laptop, or an ultraportable laptop or netbook). This choice is going to have the greatest effect on the components you choose. The smaller you go, the fewer options you have and the more you have to sacrifice. The larger you go the less mobile you'll be, but you won't be without power. Choose wisely, or, if you're not sure, come back to this section once you've assessed your other component needs.

LOW END Small size is the most important factor in your decision, and you're willing to sacrifice pretty much anything to get it.
MIDDLE OF THE ROAD You want a good mix between performance and portability/compactness.
HIGH PERFORMANCE You need the fastest machine possible, and that's all that matters.

Motherboard / Ports and Expandability

Your motherboard/logic board (the big board that connects everything in your machine) is going to determine the capabilities of your machine. If you're building a computer, you'll need a motherboard that can support your CPU and interface with other components in the machine. This is often a fairly straightforward choice, but the thing to consider regardless of if you're building or buying is the type of ports provided on the motherboard and the expandability it provides.

Consider how many USB peripherals you're going to want to connect, whether or not you're going to need an additional interface (like eSATA or Firewire), and if you're going to need to be able to add additional ports/functionality via PCI Express/ExpressCard/etc. slots. If you're looking for high levels of expandability, lots of ports, or extreme performance, you're automatically ruling out compact and highly portable machines. If you're satisfied with a minimal number of ports and expansion options, however, you may prefer tradeoffs.

LOW END You only need a few USB ports and not much else.
MIDDLE OF THE ROAD You need a range of ports and want the option of expandability, though you're not sure you plan to add anything.
HIGH PERFORMANCE You need tons of ports—the fast the better—and as much room for expansion as possible.

CPU

Your central processing unit (CPU, or your computer's brain) is going to be pretty fast regardless of what you get. For example, you can pick up a (relatively) old Core 2 Duo and still end up with a pretty speedy machine. Alternatively, several newer processors can provide you with even faster speeds and often lower power consumption—but at a greater cost. With solid-state disks (SSDs) becoming more affordable and often responsible for a bigger performance boost and perceived speed increase than a simple processor upgrade, putting your money behind more gigahertz isn't necessarily the right choice.

We'll get into SSDs more in a little bit, but the important thing to consider here is this: putting money into a high-end CPU is only really well spent if you're going to be squeezing every last ounce of speed out of it. If you're on a limited budget, you may be better off getting a slower CPU and putting the money you save towards an SSD, a better graphics card, or peripherals that will expand the functionality of your machine in more beneficial ways.

LOW END You're using your computer primarily for the web and plan to do very little work with rich media, or you're simply more interested in perceived speed rather than actual processor speed.
MIDDLE OF THE ROAD You want a fast machine but without consuming too much power/sacrificing battery life or spending too much money.
HIGH PERFORMANCE You're a video editor or just need to do a lot of video encoding, are using this machine as a digital audio workstation, are editing enormous images, or have any kind of work that'll use all the processing speed it can get.

GPU

Graphics performance requires making quite a few choices, since graphics processing units (GPUs, or a dedicated processor for graphical operations) come with so many different options and benefits. First of all, you have to choose between integrated and discrete graphics. Integrated means the GPU is built into the chipset (the motherboard). This almost always points to poorer graphics performance, but allows for lower power consumption and more compact builds (which is far more useful in laptops than desktops). The nVIDIA ION/ION 2 platform is one example of a very high performance yet integrated GPU. The unfortunate tradeoff, however, is that you cannot use it with Intel's new Core i-series processors. If raw CPU speed isn't as important to you as compactness or ultra-portability it's a good option. If you need more out of your CPU and/or GPU, however, you're going to want to look at discrete graphics cards.

A discrete card exists outside of the motherboard as a separate component. It'll draw more power but it'll almost always give you significantly better performance. There are so many factors that play into what graphics card to get that it would take to long to get into it all, but generally price and performance go hand in hand. If you need a really high end card, you're going to end up paying quite a bit more for it. This may also be a place where you'll consider upgrades important as graphics cards update and outpace themselves fairly frequently. In addition to raw performance, you may also want to consider additional features the card offers. For example, many graphics cards provide boosts in the encoding and decoding of H.264 video (one of the more popular video-compression types these days). Some GPUs can also be used by Flash, your operating system, and other software (that isn't necessarily graphics-oriented) to accelerate performance. If these sorts of performance boosts are more important to you, you'll definitely want to look for cards that can provide them. Some integrated GPUs have these features as well, so if these features are more important you may be able to save some money by using an integrated option.

One last thing to consider in the graphics department is output. If you're building or buying a desktop computer you want to make sure that a) its display connectors match what you need (e.g.: it has HDMI out if you want to connect to an HDTV) and b) it can support the resolution you need. This is less relevant with a laptop, but if you're planning on connecting an external display now and again you want to make sure your laptop's video card has a compatible connector and supports the resolution you need as well. Often times your graphics card will seem like it can support certain resolutions, but it's not always obvious just by looking at it (e.g.: DVI and Dual-Link DVI look pretty much identical but support different maximum resolutions). Just be sure you know what you're getting into before you commit.

LOW END Light gaming and graphic work is all you'll really do, so even a low-power (and probably low-performance) GPU will be just fine. You'll take whichever integrated graphics solution best fits your other needs.
MIDDLE OF THE ROAD You need the power of a discrete graphics card for games or graphic work, but you don't need to go all out.
HIGH PERFORMANCE If this is a gaming rig or you're dealing with 3D rendering of any kind, you really have no choice but to go all out on your graphics card.

Audio Card

Most of the time the audio input and output that is included on your motherboard is going to be sufficient. If you're planning on building a digital audio workstation (DAW) or just want nice surround-sound capabilities for a home theater PC (HTPC) or gaming rig, however, you may want to consider a little more. On the high end, there are plenty of audio cards you can simply install and get what you need. What's also great, however, is that if you still want higher-end audio but don't necessarily want to (or can) add it permanently, there are tons of external audio interfaces that connect via USB and Firewire at your disposal. You can easily add surround sound, studio monitors, microphones and more to any type of machine. Fortunately there are hardly any trade-offs in what you can do with audio unless you absolutely need really high-performance gear.

LOW END Generally you'll just be using my headphones or a pair of computer speakers, and if you need to record any decent audio you're willing to pick up a $50-100 USB condenser microphone.
MIDDLE OF THE ROAD You're either okay with adding a separate mid-range audio card to your machine or buying a good, external audio interface.
HIGH PERFORMANCE You're building a DAW and you need the best of the best in audio.

Hard Drives and SSDs

Generally if you ask anyone (like us, for example) they'll tell you that upgrading to a solid-state disk (SSD, or super-fast flash memory in disk form) was absolutely worth the money. Comparatively, regular old hard drives (HDDs) are pretty slow, and SSDs can make your computer feel so much faster that it's almost hard to believe the difference. Still, you'll pay significantly more for an SSD and end up with far less disk space. This leaves you with a few considerations.

If you need more than 256GB of disk space and don't have an endless supply of money, an SSD is probably not your best option. On the other hand, because SSDs are small you can often build even a compact machine that houses both a 3.5" hard drive with a capacity of your choosing and an SSD as well. The SSD can run the operating system and house your applications and you can relegate a separate, less expensive and capacious HDD to file storage. If you need massive amounts of space, traditional hard drives are going to be inevitable. While they may not provide you with the speed of an SSD, they will save you a bunch of money and offer up several times the storage capacity.

As one last compromise, there is now such a thing as a hybrid drive. It's a lot cheaper than an SSD because it is, primarily, a traditional hard drive. What it adds is solid-state flash memory and uses it as an extra large cache for the regular hard drive. While it won't amount to an enormous speed increase, or give you (what we believe to be) the added reliability of a SSD, it's a nice performance boost for a lot less money.

LOW END You're fine with the performance of a traditional hard drive and don't necessarily need a lot of space.
MIDDLE OF THE ROAD You're either fine with the size limitations of an SSD or the bulk and speed limitations of having one or more hard drives to meet your needs for high capacity storage. Alternatively, you could be happy with a hybrid drive as well.
HIGH PERFORMANCE You want the speed of an SSD and the storage capacity of a traditional hard drive, so you really need both.

Optical Drive

The optical drive is a pretty simple choice: do you need one or not? If you're building a desktop there's really no harm in including one since you'll likely have the room, but you could also opt to use that same space for additional hard drives as well. If you have the space, it'll really only cost you about $20 for a fast DVD-rewriting optical drive. The only really high-end configuration you're going to find here is if you want or need Blu-ray support for your work or entertainment.

LOW END You do not want or need an optical drive.
MIDDLE OF THE ROAD You want or need to write and read discs.
HIGH PERFORMANCE You need Blu-ray.

Network Connectivity

Network connectivity is another easy choice. With the 802.11n standard ratified and Gigabit Ethernet being more common than not, you don't really have to choose between slower and faster speeds for your network. All you really have to decide is if you want/need both Ethernet and Wi-Fi. The high-end really only involves adding multiple Ethernet ports for those of you who need to connect to multiple networks at the same time. Fortunately, whatever kind of network connectivity you need you can pretty much get without any major drawbacks (with the exception of some ultraportable laptops).

LOW END You're happy with just Wi-Fi or just Ethernet, depending on your situation. You don't need both.
MIDDLE OF THE ROAD You want or need both Ethernet and Wi-Fi.
HIGH PERFORMANCE You not only need both Wi-Fi and Ethernet but you need multiple Ethernet ports as well.

Card Readers

Card readers are becoming the new disk drive, and most computers are shipping with card readers that can, at the very least, read SD cards. If you take a lot of pictures or have any number of devices that utilize flash cards of any format, card readers may be an important consideration in your buying or building choices. Fortunately this is cheap to implement in a computer you're building and nowadays card readers are common in pre-made machines. If your machine is without a card reader, picking up a USB external is cheap as well. Your only real consideration, if you need a card reader at all, is whether or not you feel the need to have it built in.

LOW END You don't need a card reader.
MIDDLE OF THE ROAD You're fine with an external card reader or just the limited card reader that's built in to your machine.
HIGH PERFORMANCE You're need to read everything from SD to CompactFlash and it needs to be built-in to your computer.

The Scorecard

Did you end up with mostly low end, middle of the road, or high performance components? Whatever dominated your choices, we've got recommendations below.

Low-end Options

The low-end options vary because you're making the most sacrifices. You're either making sacrifices for portability, to save space at home, or to save money.

The Ultraportable Laptop - You're not looking to build a fast computer so much as you're looking for a travel companion. Depending on your budget, you're looking at a netbook or somewhat higher-powered 11 to 12 inch laptop (such as the MacBook Air).

The Mini Desktop - If you're looking for a little server, a home theater PC (HTPC), or just a small desktop for work, you have a ton of options for compact desktops. Pretty much every manufacturer makes one, from nettops to the somewhat more powerful (but equally compact) DELL Zino series to higher-powered mini options like Apple's Mac mini or a larger but still mini tower from pretty much any PC manufacturer. If you're building a mini PC, there are several cases you can start with like this LIAN LI PC-Q08B Mini-ITX Tower.

Cheap and Bulky - If price is your main consideration and you don't really care about much else, you can pick up or build a bulky but working machine for very little money. Alternatively, you could consider just buying a used machine if you really just need any computer.

For People in the Middle

You're really in the best shape if you fall into the middle because you're getting the best of both worlds. On the other hand, you're not fully satisfying either of the larger desires for portability and performance. These days, however, you're going to end up with a pretty decent machine no matter what and the middle-of-the-road desktops and laptops tend to be nearly as powerful as their high-end counterparts.

The Average Laptop - While your standard laptop sizes generally vary from 13" to 17", your middle-of-the-road option is the 15". It's often the perfect compromise. 17" tends to fare better in the higher-end category because there's usually little sense in carrying around a bulky machine if you're not getting a significant performance gain. On the other side, 13" laptops tend to max out at lower performance. A 15" laptop will generally net you the best of both worlds and are generally fairly upgradable (as far as laptops go).

The Average Desktop - An average desktop is one that provides an excellent level of performance and can be easily had or built for under $1,000. If you want to check out a really excellent build for around $800 (minus the SSD and extra RAM), our Hackintosh is a great place to start (it's a good build whether you want to install Mac OS X or not). A regular-sized tower can provide you with so much room to expand as well, so if you ever feel the need to move beyond an average desktop (which is often a pretty powerful machine already) your upgrade path is already in place.

Going All Out

The high-end is generally for people with money, but that's not always the case. High-end rigs can definitely get pretty pricey, but they don't have to break the bank.

The Media Professional - A fast CPU, a decent graphics card, and an SSD will make the performance of this machine. You'll need a fast processor to handle media encoding and other intensive tasks you'll throw at the machine, a decent graphics card to tackle the rendering of large images, and an SSD to keep you working quickly.

The Gamer - Gaming PCs are among the most expensive and the most powerful. While you certainly need ample hard disk space to store your games and a fast CPU to keep things moving quickly, your graphics card (or cards) are going to make the biggest difference. This is obvious, but when putting together a gaming rig you should plan for (at least) two things: 1) build a machine that can handle more than the game with the highest system requirements that is currently on the market, and 2) make sure you'll be able to upgrade the machine for several years. Because gaming rigs can get so pricey, you don't want to be buying a new one every time the machine skips a few frames.

Cheap But Powerful - Depending on your needs, you don't necessarily need to spend excessively to get a high-end rig. If you need extremely high performance in one area, concentrate your build (or purchase) on that area and cut corners elsewhere. Are you encoding a lot of video? Put all your money into the processor (and any hardware that will accelerate encoding speeds) and spend a lot less money on your other components. If you just need a snappy system with a ton of storage, you can generally get a decent processor, run the OS off an SSD, and use traditional hard drives to handle the bulk of your storage. If you need a powerful machine but your needs lie in a particular area, be creative with your spec list and you can get the power you need without emptying your wallet.

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What's your ideal desktop or laptop spec list? Post it (and why) in the comments.