My PSU is a 750W Corsair.
Now I think I need to start a new topic [or edit?] for Modern Warfare 2! I didn't have the latest drivers, but I updated to 9.11 and Gears runs fine now!
I've been getting stuttering in MW2 as well. Although I am not the only person it seems. I've done some googling and I even read someone with GTX280's getting stuttering! My friend has the same memory and CPU as me, but he has an 8800GT and he gets the same thing as well. It still happens, but it said it helped him when he turned down the AA from 4x to 2x. TBH, that's not really a solution for me =/