IMO, I don't think a top end card like an x1950 is worthwhile on an AGP platform.
Noting from your sig, You're running a P4 at about 3ghz. So that's fairly similiar to my last socket A rig, a DFI Nforce2 board with a mobile barton clocked at 2.6ghz with 2x512mb TCCD at DDR500. I had an X800XL back then, and I really think that the card was being held back by the memory and the CPU.
I was looking at some of the performance numbers that an X800XL PCI-E pulls in the reviews, and they're quite a bit higher than mine on an old AGP rig. Thats not so say you won't have any improvement, but it's probably more worthwhile to save for a platform upgrade (or maybe go shopping on the forums and buy something older second hand, like a 6800GS or X800XL or something).