Perhaps, but massively overpowered and will be hugely CPU limited.
I did a test run with my Barton 2500 once upon a time using an X800XT using the X3: Reunion benchmark.
With a 9800Pro, this was limited to 24fps with everything on low (resolution was 1280x768). Cranking up all the graphical detail to maximum at the same resolution, with 4xAA/8xAF with the X800XT resulted in 25fps. This was with the Barton at 2GHz. The only way to improve framerates from there was by overclocking the Barton. At 2.4GHz, I was up to 31fps with all the detail/IQ at maximum.
This limited set of testing would suggest that an X800XT or similar will be the logical limit for most DX9b games out there when running with an Athlon XP (Barton) at even 2.4GHz.
However, if you're upgrading, I would actually suggest getting a DX9c-class card which may play games like Bioshock and Mass Effect (albeit at comparatively low resolutions). Something like an Nvidia Geforce 7600GT would do the trick: it's light on power and only slightly not as good as an X800XT, but has the benefit of DX9c which the X8** series do not. Going up a level to the Radeon 1650XT series and they don't have the butch of the X800XT or 7600GT. The only real consideratiosn beyond that are the Radeon 1950Pro or an Nvidia Geforce 7800GS of some description, both of which will be massively overpowered for what our poor little Athlon XPs can churn out. A 3850 would be like sticking a fibre channel SCSI RAID system on the PCI bus of a computer.
X800XTs can be had for £20 on MM, Radeon 1950Pros for £45-ish in the same place. Nvidia 7600GTs are like hens' teeth on the second hand market because they're that good, but can be had for about £60 *** making them a non-sensical buy new when other stuff like the 1950 Pro is cheaper.
Clever money might sit with the 2600XT on an AGP platform as this would let you good with Blu-Ray and other HD content without the CPU hit. However, as a graphics card, the 2600 series is pretty rubbish, being only slightly faster than the 9800Pro in a lot of situations.
Ah - just realised you won't have access to Members Market for a while. Give me a buzz on the email in my trust.