This is a moot point, but i don't know why list it as needing a certain wattage on your PSU. I had to replace mine when I got my 9600xt, and I actually went from a 400w to a 350w. The trick is that you need a certain amperage on your +12v channel. My old one was 11A. My new one is 17A and i haven't had problems since.
I'm sure that it's the same thing with the new nvidia cards, and it's probably worth warning people that if you buy a cheap power supply with a high wattage, you're going to get something that is a POS with a low amperage and it's going to freak out.
edit: Also should I be the first one to ask what happened to TF2?
This comment was edited on May 10, 15:13.