The 6600GT is by far the best choice on bang/buck ratio. If you get the PCI-E version, you can move it to an SLI mobo later and "doubleup" the video cards for a performance boost, extending the life of card.
NVidia GeForce 6600GT (agp) review on HardAvenue.com
Note the 9800 in this review is the XT, not the Pro - the Pro would fare even worse.
[ 12-18-2005, 12:18 PM: Message edited by: Sir Krustin ]