Save your money for a Gf FX5900 and upper.
The series FX5200~5800, are sort of 'in-between' cards, which came out during the 'transition' phases between Gf4 and GfFX - they're not bad, but not really cost-efficient. One would rather buy the best of Gf4 Ti cards, than FX5200~5800.
Now, as for FX5900 and upper, it's a new ball game. The prices are dropping, but it's still a little bit expensive... but, it's worth the money invested. (Although the card is huge, with generally two cooling fans and a lot of noise..)