ATI over Nvidia for mid-level
Although I'm a die-hard Nvidia fan, I must say that for a mid-level card that has the potential to reach clockspeeds close to high-level cards, I'd definitely go with ATI (especially the x800 gto series [agp of course]). This card features 12 pipes and because some of the parts are from highend cards the overclocking possibilities are insane. Even if you don't overclock, it's a very stable card and won't overheat as the mid-level nvida cards tend to so often... (and if they don't, they make a hella-lot of noise in an attempt to stay cool).