I would go with a Nvidia 7900GT 256 or 512 MB PCI-E GDDR3 RAM setup. That is a VERY powerful card and it costs less than $300 now and can even be used in SLI mode with another of the exact same card to give you up to 1 GB of video memory. That card runs very cool compared to any ATI card and higher level Nvidia cards so your PC should not get over heated. The fan on it is a bit loud but you can swap it with a more silent one that cools it just as good. I'd go with the 512MB over the 256MB setup since the extra RAM will help out with future games and with upgrading.
Make sure you go with a new conroe processor from Intel. I just got the 2.4Ghz duo core 2 with 4MB cache and it outperforms even the highest end AMD processor out there right now on just about every benchmark and outperforms a 3.7Ghz Extreme Pentium 4 by a mile in ALL benchmarks and uses WAY less power to boot. The way of the future is duo core processors that work smarter and faster at lower GHz levels. Although you should look at it like 2 X 2.4 Ghz processors working together making it more or less a 4.8 GHz monster. That processor right now retails for about $500 and the highest level duo core right now retails at $1000 but I think it's a bit of a waste for an extra 300 MHZ per processor (600 MHZ faster, big whup
). So anyways you could more or less get a VERY powerful PC for right about or even a little less than $1500 if you wanted. Good luck and happy hunting!!!