His Phenom is the problem, you must be joking....? Its a quad core, that 2.2ghz is around an effective 5.3ghz. If it was a 2.2ghz P4 then thats what would be causing the troubles. Even a E6500 is just fine for this game.
Anyways, I have a 8800GT oc'ed to 700mhz and I run at 1680 x 1050 on the Medium preset with 2x AA and AF at 8, with shadows turned off (there is very little loss to visuals with shadows off compared to on with low detail). Before turning shadows off I was averaging around 50fps, after i turned shadows off im averaging around 70, 100 indoors. The 8800GT or the G92 GTS will get the job done, but like others said I recomend waiting for the ATI 4870, screw the GTX 200's.