You can get the cpu fan speed low using "smartfan" in the hardware monitor section which is found on most newer boards. Either calibrate it or use manual settings; lower numbers will reduce the speed. I then set it to "quiet" mode which your board may have.
fluid dynamic bearings are silent and can run up to 100+cfm with little more than wind noise so check them out over ball bearing or sleeve bearing fans...
coolermaster hyper 212 is cheap and works. but the fan that comes with it is noisy. so i suggest you swap it out for FDB fan... like the Arctic Cooling F12 PWM Case Fan 120mm
yes its a case fan but its 2000rpm silent and pushes 75cfm.