Use the following guidelines when choosing a case:
If you are migrating an existing motherboard, buy a case to fit that motherboard. If you are building a new system, buy a case that accepts full ATX motherboards, even if you're installing a Mini-ATX or microATX motherboard. A full-ATX case allows upgrading later to a full-ATX motherboard, and provides more working space even if the system will never have anything larger than a microATX motherboard installed.
Choose a case that leaves at least one or two bays?ideally 5.25-inch external bays?free for later expansion. As the price of tape drives, DVD-ROM drives, and CD/DVD burners continues to fall, you're likely to want to install one or more of them in the future. That's impossible without free drive bays. A mini/mid-tower case with three external 5.25-inchbays, two external 3.5-inch bays, and perhaps one or two internal 3.5-inch bays is usually the best compromise between size, cost, and available bays, although a full tower may be the best choice if your current configuration fills or nearly fills a mid-tower. Some cases can be ordered with two or three optional internal 3.5-inch bays for very little additional cost, typically $5 to $8. If in doubt, always buy the next size up.
It's always tempting to save money, but cases are one place where it's easy to spend too little. The cheapest cases ($30 or $40 with power supply) are often unusable due to misaligned holes and so on. Even midrange "name-brand" cases often have razor-sharp edges and burrs, which can cut you and short out wires. Expect to pay at least $35 (without power supply) for a decent mini/mid-tower case and $50 to $60 for a full tower. Paying 50% more than that usually gets you a much better case.
Many cheap and midrange cases include a "throw-away" power supply that's of poor quality and undersized. If you have such a case, do yourself a favor: discard the bundled power supply and install one of the power supplies we recommend in Chapter 26. At best, cheap power supplies cause reliability problems. At worst, we have seen cheap power supplies fail catastrophically, taking the motherboard and other system components with them. Better cases may be available with or without a power supply. If the standard power supply is appropriate, you may save a few bucks by buying the bundle. Otherwise, buy only the case and install a high-quality power supply sized appropriately for your needs. Standard power supplies fit standard cases interchangeably, so compatibility is not an issue.
Heat is the enemy of processors, memory, drives, and other system components. Cooler components last longer and run more reliably. A processor run at 50° C (122° F), for example, will last only half as long as one run at 40° C (104° F), but twice as long as one run at 60° C (140° F). The best way to minimize temperature inside the case is to move a lot of air through it. Although the power supply fan and processor fan may provide adequate cooling on lightly loaded systems, adding supplemental fans can reduce ambient case temperature by 20° C (36° F) or more on more heavily loaded systems. Many cases can be ordered with optional supplemental fans. If the case you order offers optional fans, order them. Otherwise, add the fans yourself. You can purchase supplemental fans for a few dollars from local computer stores and mail-order suppliers. They are available in various standard sizes from 60 mm to 120 mm, so make sure to purchase the correct size. Note that many cases that accept multiple fans use different sizes in different locations.
If you frequently add and remove components, consider purchasing a case with accessibility features such as a removable motherboard tray and drive bays. If you don't open your case from one month to the next, you may be better served by a case with fewer accessibility features, which is likely to be less expensive for equivalent quality and rigidity.
When you compare case prices, remember that the cost to ship a case can be substantial. Cases you find at local stores already have that factored in. Mail-order companies may charge $20 to $40 to ship a case, or even more for heavy full-tower cases.