I'd go with a thermalright heatsink. They're generally regarded as the best (other than water cooling) by gamers and overclockers, and the heatsinks are good enough that they'll sufficiently cool a non-overclocked system with no fan. I've got a thermalright slk-947U, and it keeps my amd xp2500+ at 35 degrees. I'll also mentioned i've got my chip overclocked to 3200+