I've had a 92mm fan on my former rig, it was a bit louder than expected, and didn't dissipate the heat really well, my Phenom II X2 545 had 40 degrees C on idle, so I thought, a CPU with 95W TDP might only be cooled adequately by a bigger cooler ... But thanks for the advice, I'll save a lot of money not buying something senseless.
Was your "former" 92mm fan heatsink a tower-style one? If so, I'd suspect a mounting or ventillation problem, if not then 40C idle is...more in the range of a downward-flow HSF. If silent operation is really high priority, I would suggest a 120mm tower-style HSF. It will be overkill as far as cooling is concerned, but that also means that the fan will spend most/all of its time at min RPMs which will generally be quieter than a 92mm fan at min RPMs.
That being said, a good quality 92mm tower-style HSF like the Noctua is likely to be just as quiet, although you'll have to decide whether or not its worth almost twice as much. (since its not PWM, you can also force the Noctua fan to run at min RPMs regardless of the cpu temp with their included in-line resistors.)Hardware Secrets
has a pretty extensive list of HSF's tested. Unfortunately they oftentimes
only graph temps, the rest you have to look at in their table above. The Hyper 212 EVO has a strong showing in their tests, maybe a little too strong...
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