What PSU do you have? It may limit your choices due to power constraints. Otherwise, check Cleeve's thread, "The Best Gaming Video Cards for the Money."
Seems to me in your $200 range something in the x1950-family would be good. They should outperform the 7900GS I just bought, but I think I spent only $149.
Well, in that case, $300 for an 8800 GTS is a better investment than $200 for an x1950xt IMO. It depends on how strict that $200 budget is. The GTS may become cheaper around Thanksgiving too, if the new nVidia cards show up on schedule.