Thermaltake Ultra 120 heatsink + Scythe flex 120mm ultra-quiet fan > all. Not cheap, but it's bar none the best damn combo I've ever seen (and reviews point out that it's both the quietest and best-cooling of the sub-$100 bunch). I also have a Zalman 9500 copper standard model in my main gaming rig that works very well, too, though it doesn't cool as well as the thermaltake.