When buying a case, make sure it is matched with the motherboard. ATX is a newer design, released by no other than Intel. It is not mainstream yet, but it is gaining in popularity. The openings in the case are built to align with the ATX motherboard, and the power supply is specially designed to be software controlled. Many other advancements are built into the case, making them fancier and more expensive.
All cases have the power switch and the reset button.
Power switches come in different designs, from the push button to the toggle switch. Many cases have a turbo button. This button's job is outdated and the button is really pointless on modern machines. Many think that pressing this button puts the computer in some super-duper fast mode. In reality, the opposite is true.