THERMALRIGHT ULTRA-120 EXTREME
http://www.thermalright.com/new_a_pa...66rt_revc.html
sometime ago i went searching for a q6600 cooler and narrowed it down to this and a Noctua; i went with the Thermalright (the 775 model), i assure you this is a great choice.
it's probably the king of bang-for-buck in cooling; it's affordable and it's high end air cooler, actually better than most and more expensive ones; it won't get much better, you'd have to go for a monster Noctua, more expensive, and a few degrees cooler.