I'm looking for the most quiet CPU cooler available for the Intel i7 870 2.93ghz (LGA 1156).
I will not be over clocking, but it is common for my room to reach 28 degrees Celsius during the summer. My case is the Antec P280 and I have 2 intake fans on the front and 1 exhaust fan on the back (all Noctua NF-S12B FLX running at 1200rpm). The top fan slots are blocked with duct tape.
I'm not sure what is most quiet but I can tell you that I used a coolermaster 212 and set the bios such that it ran at ~1000rpm and it was quiet. I was running a email@example.com and the 212 kept it cool (and quiet).
CM Hyper 212+ or 212-EVO, costs $25-35 and are the best HSFs currently on the market under $60.
My 212+'s fan is at 700RPM under load and that keeps my CPU under 55C.
My case has two filtered front intake fans, one rear exhaust fan, all three set to low-speed. (They are tri-speed fans.) My computer is nearly silent fan-wise but I will be kicking front fans to medium-speed once room temperatures start hitting 30C this summer, which is going to make things somewhat noisy.
I have used both and I have not noticed a significant difference. Save your money and go with the 212.
The main reason I see for using a Zalman 92mm HSF would be if the 212 doesn't fit in the case or on the motherboard... the 212 is pretty big and does not fit in all cases, it sticks out a few millimeters in some.