I have the same setup pretty much. I can play crysis On vista (DX9) @ 1600x1200 with no aa and pull 25-40 FPS sometimes with motion blur off. The only thing is wrong is that DX10 ns like **** no matter how low the res. IF you game on DX9 @ 1600x1200 your cpu isnt going to do much work. I think that it is very playable on my rig. I got a Quad on the way it should be here in 2 says.
and a low of 28