Seasonic X-Series SS-460FL: 460 Watts of Fanless Power
 

The 460FL is based on the same design as their new 850W model, but they've changed some components and put in some additional heatsinks. The topology remains the same, with the major difference being the removal of the Sanyo Denki fan and the fan control. You also get fewer connectivity options, though there are still two PEG connectors for graphics cards which is pretty good for a passively cooled PSU. Pricing on the other hand is quite steep: $160 online, which is in the same ballpark as high-end 800W and larger models! Then again, if you're looking to build a silent midrange PC, you wouldn't want to start with an 800W PSU that only gets 75% efficiency on an 80W idle PC load.

http://www.anandtech.com/show/3962/s...l-460w-fanless