Quiet/Silent HSF suggestions

[deimos3428]

I'm currently using an H50 with dual Noctua NF-P12s exhausting, which is great performance-wise. The fans don't make much noise as they're at the back of the case and undervolted in software to ~700rpm. The case is a Lancool K58 with a lot of quiet airflow via two NF-14 140mm exhaust fans in the roof, NF-P14 140mm + NF-S12 120mm intakes, all operating at 5V so they're about as quiet as possible without turning them off. The PSU is bottom mounted, sucks air through the bottom and out the back and is neither audible nor involved in the airflow of the rest of the case.

The problem is when I drop the fan speeds, I can hear the annoying buzz of the H50's pump, which is quite audible even when undervolted as much as possible. (I've actually been turning the fans back up slightly to raise the noise floor and drown it out with a more pleasant woosh.)

So as much as it pains me, I'm looking to replace the H50 with something quieter that can still chill a stock Phenom II 955. How much of a temperature hit would I take by moving to a dual-fan Hyper 212? Could I get away with a passive solution using just the case airflow? Any suggestions are welcome.

[boost]

So as much as it pains me, I'm looking to replace the H50 with something quieter that can still chill a stock Phenom II 955. How much of a temperature hit would I take by moving to a dual-fan Hyper 212? Could I get away with a passive solution using just the case airflow? Any suggestions are welcome.

If you get a better air cooler than the Hyper 212 the temperatures won't raise.
Thermalright is the best, but expensive:
Thermalright Archon with two fans.
Thermal right HR-02 with one very slow fan.
For a more budget friendly solution take a look at the Recommended Hestsink List.
Scythe Mugen 2 or it's sucessor Yasya are good, so is the Hyper 212, but it needs a fan replacement for silence.
Passive cooling for one of the hottest CPU probably won't work.

[deimos3428]

Thanks for the reply, I'll peruse the list and see what I can come up with. I'd prefer to take a temperature hit (15 to 20C) over adding a massive cooler like the Archon, though. I'm trying to find the smallest/quietest solution that can still keep under 60C or thereabouts. If all else fails I'll pickup a fan controller and try lowering the pump RPMs further.

[sub]

or a Noctua D14, very good in passive mode too