Your RAM might also be a bit of a bottleneck. If you want to compliment that 8800GT, I'd look at getting at least moderate latency DDR2 800 RAM (in dual-channel for best performance), and a Core 2 series proc. Not necessary to upgrade, but if you're looking for something to match and maximize your performance gain, I'd recommend RAM over processor, but both are going to bottleneck. Those three (RAM, GPU, CPU) tend to go together when you're talking about performance gain; if you want to get the most out of one of them, you want an equivilent generation of the other two.