while the cpu might consume quite a bit because it's a quad core,I believe the 8800GT doesn't consume as much power as you think, less than a GTS even. I'm using a 520W supply with my setup, and as well as an O'ced processor and an 8800GT, I'm also running two hard drives, a DVD drive and four fans.
Now I know this isn't really *that* much lol, it's more than enough to power the 8800GT