I'm surprised this wasn't mentioned, but a lot has to do with proper airflow. Some cases are actually very poor for proper airflow. Other's are truly fantastic! You need to do some research. I did, and found the best case I could buy at the time was at Fry's Electronics for around $150 for a full-tower. A standard metal case mid-tower has one fan with airflow going out on the left hand side, and one or two fans on the back pulling air in, not including the power supply. That is a poor, poor design flaw if you have a good video card (or two). A mid-tower should be able to house all your peripherals without any issue, but the airflow is paramount to having your system run without any problems from now into the near future, if you have a video card worth a damn that is 
. FYI, the cases I was reviewing also had air intakes on the top and front and worked 60-70% more effeciently than your standard mid-tower with a metal case (so they claim).
. FYI, the cases I was reviewing also had air intakes on the top and front and worked 60-70% more effeciently than your standard mid-tower with a metal case (so they claim).
"The true value of a human being is determined primarily by the measure and the sense in which he has attained liberation from the self." -Albert Einsetin