I have the ZALMAN CNPS5X. It is supposed to be 20-30+ dB. Mine certainly is. It is the loudest fan in my system, even on the lowest RPMs. Since I can't change the fan out, I'm going to replace the cooler. Quiet is more important than tremendous cooling, though I do plan to experiment OCing my i5 3570k. My current temps are around 32.
I have heard that the Coolermaster Evo is really quiet. Their info says on low speeds, it is around 9dB. That is an option. But I've also heard that some of the simple closed loop liquid cooling solutions like the h55 or h60 are very quiet too. And I know I can replace the fan(s) on those if the stock ones are too loud.
I know that Noctua fans are quiet too, but I have a nice open panel on my case and frankly, the color scheme on the Noctua fans bugs me more than it probably should.
So is the pump on the corsair liquid systems + fan quieter than the 212 hyper evo? Or is there something else I should be looking at?
Buy the Evo with a silent 120mm fan and you'll be more than happy and it will not break the bank in any respect. Mine has two silverstones bolted to it and with them at under 1000 rpm there's still nice airflow and I hear the PSU running.
People can get completely wild with quiet solutions, the problem isn't the heatsink, it's the fans. The Hyper 212 is a great piece of work and arguably the best on the market especially for price. The stock fan can be loud at 2k+ RPM, but so will ANY fan at those kind of speeds. You move air, it's going to have resistance in the air and off of things inside its path so it's going to make noise. Key is finding that happy medium. That's why I went with 110CFM silverstone fans for myself. I'm absolutely serious when I say at 600rpm, my 212 cools well enough for almost any situation aside from MAYBE IBT and 24h Prime and the thing is quieter than the vibrator in my cell phone.
Slower the fan, the quieter it will be, the heatsink doesn't do much to change that fact.