Yeah the one David is suggesting is a better card yet if your motherboard is AGP, you'll need a bridge chip to change the PCI-E to AGP for that card. But this is for top gamers who want the best.
The new ATI card though, the X850XT PE is the fist ATI AGP card for high gaming
and that card is also good but is only needed if you want to play at top settings again, and really high resolutions that some monitors don't even support. If you are a really dedicated gamer, then yes, People would pay that much for a card, and will play games at their best for a while.
I would personally go with the 6800 if you wanted to pay that much for a card, which will be about the same I think to the X800, but it's your choice, they are both good cards. Then theres the 6800 Ultra which is as good as/ or better than the ATI x850 David was saying about