My favorite brand of power supply is ULTRA and TurboCool Ex.
For a high end system look for 550-600 watt power supply.
I just bought a 600 watt Ultra Premium power supply with a true wattage tester to go along with my new BFG Tech GeForce 6800 GT OC.
By the way, with the same exact setup(two machines) with a 6800 GT and an Ultra, the benchmarks were only 300 points less on the GT compared to the Ultra.Not a big margin if you ask me.Well worth the money, and a lifetime waranty!
Props to Nvidia...