Thanks again for all the input, y'all.

Decisions, decisions

Looking more like the extra $20 for the 8800GS would be worth it, but I wouldn't be shooting myself too badly in the foot with the 8600GT either. Being on a tight budget stinks
Guess I should have stated that I was running XP also, but good to know that Vista isn't a problem for either (other than Vista's own "little" problems).