If you can stand to wait I would say that would be the best bet. The radeon 9200 isn't a horible card and can play most current games like HL2, albeit at low settings.
However I recently spent 200 dollars upgrading from a fx5200 to a 6600gt, and I am very satisfied with my purchase.

I saw an ad for a x700 256mb agp card at best buy for $160 whitch is very comparable on benchmarks to the 6600gt agp and will get you beter DX performance ( for games like HL2) whitch would be a great solution for your problem.