Hi Benan,
What to look for is the memory interface and number of pixel pipelines.
I wouldn't recommend the 6800XT as this is an 8-pipeline (but good 256 bit memory interface), especially if you wish to use any amount of anisotropic filtering or AA (which both help BF2 tremendously).
I originally recommended the X800GTO as it's a 12-pipeline, 256 bit memory interface card. You can crank the resolution, AF and AA without impacting framerates given this overage. Moreover, many of the Sapphire X800GTO's are 16-pipes vs 12!
The 7600 is only 128-bit memory interface, but has a full 12-pipelines. This can yield similar performance to an 8-pipe/256-bit card in many cases.. so I'd still say if you're going this route, just go the 8-pipe/256-bit memory 6800 series.
The X850 Pro is a great choice as it's 256-bit memory, 12-pipelines.. just like the X800GTO. I'd say if you can find an X850 Pro or X800GTO, you'll be golden and be able to crank up all the options in BF2 with great performance.
On the PSU, I'm unfamiliar with that case- sorry. You might be able to cross-reference your old PSU to see if it's a standard ATX though. If it is, then any standard-ATX replacement should work.