You did mention Linux use earlier in the thread, in which case ATI drivers will suck even more arse!
As for game playing, at that resolution you could probably get away with a 7300, so almost anything would be good enough. I would be tempted by a 7600GS as passive (ie no fan so silent) single slot cards are readily available pretty cheap.
You might want to check out this review of silent graphics cards. A bit old but gives an idea of how low end you can get away with at 800x600.