[aghastpumpkin]

If your only gaming, CPU choice is irrelevant. Unless your playing extremely CPU intensive games like Rome:Total War, choice of CPU makes absolutely no difference of framerates(minimally) and your money is better spent on a graphics card.

For example, a FX57 with SLI 7800GTXs may only gain an extra 0-2FPS over an Athlon 64 3000 with the same graphics cards.
Socket 939 Opterons are simply the best overclockers ever. A £95 Opteron equivalent out of the box to an Athlon 64 3000 can overclock fast enough to rival the high end £600 CPUs.
The best PCI-E GFX card (I'm guessing your pricing is about £150) would be one of the new 6800GS cards or an X800GTO.