Thermalright Ultra 120 eXtreme is the king of air coolers, the Tuniq Tower is a close second. Scythe Ninjas and OCZ Vindicators run well fanless/passive, the Scythe Infinity can have quad-120mm fans [!!!], the Noctua NH-U12F and U12P come with their uber low noise fans, and that's just some of the better tower heatsinks. Make sure to get some nice fans with it too. I'd recommend either the Scythe Slipstream or S-Flex from 1200RM up, or Noctua NF-P12, as they have excellent airflow/noise/pressure.