Well, just built a new system with a Phenom II 550 and bought a Nexus 430w PSU off of Kustompcs. Waw!!! Quietest PSU i have ever had. The PC is almost dead silent now. I have tried many PSU's over the years; Corsair, Enermax etc and this Nexus blows them out of the water for quietness. Plus, it is a quality PSU so 430w is more than enough. Nice one Kustom for stocking them!!