Actually, the lrod of all cooling atm would be phase change imo.
http://www.frozencpu.com/products/11...04-L-1052.html

But damn is it expensive, and it's really REALLY annoying to work with/on. I had the dubious pleasure of messing with one of these units, friend bought everything and wanted the fastest PC he could get. He insisted on having one of these things ... the whole smothering your motherboard in silicon so it doesn't get destroyed kinda turns me off.

Anyhow, I personally like the Thermaltake's Orb series. I use Ruby Orbs in all of my machines. They're big (big enough you have to put them in AFTER sliding the mobo tray in a Lian Li case) but they're incredibly quiet and still keep my Q6600s nice and chilly even under constant use.