I'd get a Radeon 9600 Pro and put the difference towards a nice case (no offense meant to Lasereth). Here's what you can get with the $200 price difference:
http://www.thermaltake.com/products/xaser3/v2000a.htm
All aluminum, pull-out motherboard tray, front FireWire and USB, swing-out front bezel, removable drive bays, 7 ThermalTake 80mm silent fans, Adjustable fan speeds and temp readouts, and a completely tool-less design.
That's, of course, if you want to spend the whole difference on the case. I would actually just recommend a nice Lian Li or Cooler Master case, then buy and Antec or Enermax PSU separately.
Here's a good Cooler Master:
http://www.newegg.com/app/viewproduc...tion=ATC%2D210