@Rodomoc
I actually used to use a similar board with amithlon, so its pretty likely you'll have some success with it. Two pci slots could potentially make things trickier, but if you can get either sound or networking supported through linux side drivers, or find a suitable pci riser card you'll be good to go.
@shaf
Unfortunately Amithlon only really supports up to 1.5gig of RAM, anything beyond that will stop it working. More realistically 1gig, but there are rare occasions where a person can get 1.25 or 1.5 supported. It's definately worth using kernel3.x or 4.x though too, although an athlonxp is old enough that you'll probably get away with 2.x and earlier kernels.
@thread
To clarify things, at the moment amithlon has no 3d hardware acceleration. There is wazp3d, but for amithlon it's only software rendered, which while looking pretty, is varying degrees of slower (depending on amount of eye candy enabled). In the future this may change, as Ratte has been working on an openpci driver for radeon cards (up to semi modern cards) that has full2d acceleration (already shown working, a few videos are on youtube), and I believe he's also planning on adding 3d support as well, which would be awesome

I dont have any "insider info" on this by the way, just what he's said, and what Ive asked on public forums like eab.