I picked up a Seasonic Super Tornado PSU after reading this review over at Silent PC Review. Seasonic claims that is is one of the most efficient PSUs on the market which Silent PC Review confirmed. It is also very quiet.
To confirm the efficiency claims, I used my handy Kill-A-Watt meter to measure the current draw of my main desktop PC PC at idle and full load using mprime. My old PSU was an Antec True 430 which sells for $65 over at NewEgg. The Kill-A-Watt reported a power factor of 0.65 at idle and load, and 107W at idle and 124W under load. After swapping out the True 430 for the Super Tornado 300, the power factor measured 0.99 and now only pulled 91W at idle and 107W under load for a power draw reduction of 15%. Having a near perfect power factor will also reduce the current draw through the house wires as well, in this case the current draw will be cut in half. As Silent PC Review also noted, I found the Super Tornado to be very quiet, I can't hear it over the CPU fan or hard drives in my machine.
I've now ordered two more Super Tornado 300s from Computer Gate at $65/ea to replace the PSUs in my Linux firewall/fileserver PC and my MythTV PC. Computer Gate has free shipping on those PSUs right now. I'll take before and after measurements of both when they get here.
I highly recommend this PSU as it's price is comparable to all other high quality PSUs on the market and has the advantage of being the most efficient and also being extremely quiet.