I had a 5600 card when i first built my computer, the fans on the heatsink eventually melted and i smelled burning so i turned off the computer. No overclocking at all, and internal temperatures (case) were around 35*. Got an ATI 9600, basically the equivalent card, same price, same specs, and the difference was just astonishing. 10-20 point fps boosts, much smoother and quicker reactions, etc etc.
Firstly, I suggest getting an ATI card, and secondly, i don’t suggest spending over 200 for it, because as with all things computer related, they either day or need to be upgraded in a few months.
and seriously, 400 dollars on a graphics card… put that towards an hdtv or a 36” monitor/tv.