AcoustiFan: DustPROOF = (Volts/cfm/dba) 12/56/25, 7/42/16, 5/25/<10
Scythe S-Flex = 12/33/8
What PSU will you be using though? As this will most probably be the loudest component. Nesteq do a nice 620W semi-fanless one (used to be called Elan Vital) is has 80% plus efficiency rating, 25A on 3.3, 30A on 5V, 12v1 18a 12v2 30a. 0-30dba - can have it manual or automatic (i.e when it reaches a certain temp fan goes on). I wouldn't like to use one on an SLI rig though having said that they do have 2 PCIe connectors so I guess they're designed for it?