Well, some people are pretty sh**ty on this board, but in general, the 6800 around 250 is a "better" buy than a 9800 for ~160.
But this is only for a very heavy gamer, because $100 is nothing to scoff at, when new dell systems often cost 400 or less.
If you are a casual gamer than the 9800 will serve you well, play all games with only some sacrifices in settings, be very STABLE, and makes good sense as a final AGP card. Chances are very high in this price range, that it is well matched to the hardware you have. For example a 6800 is kinda overkill if you are still using a 2GHz processor.
But the 6800 currently represents what is generally felt to be the best "bang for the buck" of the cards, much like the original ATI 9800 non-pro was 18 months ago for $200.
Newegg offers an XFX version that is dual DVI, which is great for 2 lcds.