Honestly, if I were you... I'd see if I could swing an X1950 Pro. It will slaughter those two cards. In fact, the 1950 Pro will even cream a 7800 GT in nearly every benchmark I've ever seen. If you look at online places such as newegg or tigerdirect, you can often find this bad boy on sale for as little as 150 bucks. It comes in AGP and PCI-E so be sure you find the right one.BUT... if you ONLY want to consider the two cards you mention, I'd go with the 6800. If I recall, it overclocks better and between the two cards, you're not going to get screaming performance on more complex games anyway so you may as well bank on the extra features like SM 3.0.