I have the same mobo and cpu with Scythe Mugen 2 Rev.B cooler. Unlike stock cooler, It's completely silent even at full cpu load but don't expect better overclocking results. It has the PWM function (the fan speed adjusts itself automatically on the fly) which not many coolers have.
However, if your main corcern is noise, any 120mm fan will do the job. A cheaper and good alternative is CoolerMaster Hyper 212 Plus, though a little louder than Mugen.