You can get an x1900XT from newegg for under $500 right now, it is a decent card.
http://www.newegg.com/Product/Product.asp?Item=N82E16814102003
But what do you use your computer for? Games? 3D Apps like Maya, or others? And what is the rest of your computer stats?
Edit: Ah, took the words right out of my mouth I see. 😀
Isn't the Sapphire one a hands down win over the others ?
They are one of the better ATI GPU suppliers of cards IMHO.
Giga-byte (in a true non-biased world) would be a close 2nd though.