xp-90....great bang for your buck, and doesn't wiegh a tonne like it's copper version, so if you carry your case around to lanparties or whatnot, you don't have to worry about it. It's really cheap at svc.com, I think
You might want to look into the Thermaltake Silent Boost K8. That is what I have, and it says it is made for Athlon processors. All I know is that it isn't noisy, and it keeps my CPU (which I have overclocked from 1.8 GHz to 2.3 GHz) at about 35 c when idle.