Cooling features are a must. I liek the Mid Tows the best. Unless you are going crazy a 250w PS will work, but a 300w is best if you can afford it. Either one MUST be AMD approved. Look how the PS is mounted. A good one will have it mounted horisontally across the top with a spot for an extra case fan in back below it. Quite a few have the PS mounted vertically and the CPU will be barried behind the PS. This is VERY bad for cooling. Notice in this picture (it is kind of confusing because it is taken from inside the case looking back at the power supply). The PS is only about 1/2" front the fan on the heatsink:
Now this guy cut a hole and mounted a fan directly above the CPU, but normally their is little way of venting the heat the CPU gives off. This is a picture of a very good case for cooling:
Notice the extra cooling fan below the PS. Also the grill allows good airflow. Most use a bunch of small holes drilled in the case. This rear picture is from the Fong-Kia FK-603 and this is the front:
It has a spot for another fan up front with the same vent holes (under the snap-off bezel). It also hase good vent holes in the back, top and front were there is not enough room to put a fan. It also has a duct connected to the rear fan to remove the CPU's heat. It even includes an AMD approved 250w PS. You can get it here for $67 (plus about $15 for shipping):
If you want something with even better cooling, then get the FK-320 for about $100. It has room for two 92mm and 120mm case fans and comes with a 300w AMD approved PS (it also comes in black):
As for drive bays. I dont liek zip drives so one is fine. room for 2-3 internal is fine for most. 35 1/4" bays are good for me. I only use 2 (CD and CD R/W). That is up to your needs. There are a lot of other features too, but most of them are really up to you... removable motherboard tray, drive rails, locking covers, removable sides, top and front, and even refrigerant cooling system (VapoChill Unit).
The COMPUTER is your FRIEND!
Happiness is manditory.
AMD Phenom II x4 945 3Ghz | ASUS M4A77TD | 2X WD 1TB SATA 2 hard drive | 2x2GB Corsair XMS3 | nVidia GeForce 8800 GTS | ATI TV Wonder Theater Pro 550 | Antec P-160 case | Antec 650w Earth Watts | LG Blu-ray Super Drive | LG DVD RW | Windows 7 Pro