Have the latest release drivers installed. Betas are prerelease (ie incomplete). You should turn Vsync off with your card, it lowers preformance darmatically (at least on my machine- dropped about 7k in aquamark with it on). If you are willing to sacrifice some quality, try turing down some of the lighting effects in CS, and possibly turn down (but not off, or you wont be able play very well) particles such as gernade blasts, muzzle somke, projectiles, ect.
AGP won\'t fit in PCI-E... unless you use a really good hammer. ~Trotter