Upgrading XFree86 is a major task in itself.
I have a radeon 9000 pro and it's supported through 3rd party drivers. It will work with XFree86 4.2 or 4.3
go to www.ati.com
and search for the drivers.
The drivers that work for the radeon 9000 are actually those for the FireGL cards, 8700/8800. Why, I don't know, same chipset i figure.
you could also go to www.schneider-digital.de
and navigate to the downloads, ati section and get the FireGL 8700/8800 drivers for 4.2 or 4.3, whichever you have.
Make sure you have the sources for your kernel before you compile the drivers, it won't work otherwise.