I know Nvidia 6800 is a good card at about that price. I had previously thought about the Radeon X800Pro, but the site that had it for $199, probably realized the mix up and now its worth $279.99, so that's out of the question.
But other than that, what are good cards at about that price?
More aboutbest graphics card range
PCI Express best deal is the X800 for 160
AGP best deal is 6800 for 150.
AGP only, cause I don't have PCI express on my mobo
I would do like scot said and stick with the 6800. It will give you the best performance you can get for that price range.