If you want the quietest case fans get the pc and power cooling silencer fans. Buy two or three of them and set them as intakes. If your rear exhaust is 80 mm as well get a silencer for exhaust as well. Also, if your ps supply fan is loud get a silencer for it too. In my current rig,supermicro 760a, i have two silencers for in take, a 92mm papst fan for rear exhaust, and another silencer in my powersupply. For my heatsink/fan, i bought some super quiet 60mm fans from phamcomputers. THey are the adda ones.