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” external bays—free for later expansion. As the price of tape drives, DVD-ROM/RAM drives, and CD 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” bays, two external 3.5” bays, and perhaps one or two internal 3.5” 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” 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 ...