If you want good performance from wine, the CPU is more important than the GPU, provided that it is a decent NVIDIA GPU. Overclocking my e5200 from 2.5GHZ to 3.5GHZ resulted in double the minimum FPS with Half Life 2 : Episode 1. I will say that the 80-100% figure is a little optimistic, though (maybe those with i5/i7 machines can reach that performance). Oblivion still runs at 15-20fps in some outdoor areas, where is it runs at 40-60fps in the same places with Windows. COD4 is still dropping into the 20-30fps range; on windows it doesn't drop below 60 fps anywhere. Perhaps that figure is true for an 8600gt, though. The card being slower might mean that is less affected by bottlenecks in wine. Just a guess, though.
