What PS did you buy? When I built my last computer I put in a Xion 600w. It had a huge fan, 140mm, so it could run slower (hence quieter) and still move a ton of air.
600w is complete overkill for what I'm running at the moment, but it was the same price as some 450w units, so it was a good buy. It's been stable as a rock and quiet enough I can hear the platters in the HD occasionally.
