Zerotherm's Nirvana NV120 vs Thermalright's Ultra 120 eXtreme
 

The Zerotherm Nirvana NV120 is a fantastic cooler that outperforms much of the competition between the very quiet to silent fan lower speeds. And, although it is technically the best performing heatsink we have seen to date, we’d never recommend using it at full speed.

http://www.bit-tech.net/hardware/200...otherm_nv120/1