If you are in the USA, BestBuy retail stores have the Visiontek X1950 pro AGP in stock for $299. Overpriced, but it's way better than a 7800GS and worth it if the rest of your system is up to par.
I'd wait for this one to appear in stock. 512MB and $250 shipped. It just may end up being the best performing AGP gaming card that will ever be made. http://www.zipzoomfly.com/jsp/ProductDetail.jsp?ProductCode=326860