Had the same problem of high temps and low fps. low like 35, running two GTX 570s
I turned High Quality Anti-Aliasing to normal and it now runs like a dream, hitting 172fps...
the supersampling murders everything that tries to touch it.
Turn that down to normal, see what happens
"So many times I wanted to move about (make poop but can't leave the game because it's online)" - Underworld