You would get better gaming performance out of either one of:
a) i5-750 + ATI 5870/nVidia 480
b) AMD Phenom II X4 955 + AIT 5870/nVidia 480
The 5850 is a fine GPU, but if you're just looking at gaming, the i7-930 isn't needed, and won't improve your in-game experience as much as spending more on the GPU and less on the CPU.
If, however, you're looking at a cross-functional gaming & rendering/encoding/editing build, it's fine.