As far as my system goes, it's a few years old.
I've got a Core 2 Duo 6600 with 2 gigs of ram and an ASUS P5B Deluxe board.
i'd upgrade the ram, but even using windows 7 i don't think i'm actually maxing out the ram I have now. This past week, i've been playing WOW windowed (which seems to help), watching a pirated movie, and/or running firefox in the background.
I was going to stay away from ATI because i'm still butthurt about the driver thing, but I can get over it pretty quickly if it really is a better card. More importantly, i didn't want to spend a fortune for a video card since, like I say, I'm pretty much only going to be playing Blizzard games (Xbox and Wii fill my other needs pretty well)
Thanks for the help guys.. you guys really helped out alot toward my decision. I've been coming to Tom's Hardware in one fashion or another for 10 years and you guys have always been super knowledgeable and friendly to an hardware-out-of-touch n00b like me