Evo,
The "sweet-spot" right now is the GeforceFX 5900XT with 128Mb of RAM and the Radeon 9800Pro with 128Mb of RAM. They are both the best bang for the buck.
If you want to save a little money then drop down to the Radeon 9600XT. (But you should find the GeForceFX 5900XT for just about the same price, and the 5900XT out performs the 9600XT.)
Take Care,
Richard