^^^This
The *nix forum should be named "All Things *nix" or something like that. Most people here (O/S) are here for Windows, with a dribble of other questions. It would be better to put all the nix stuff in one place.
To answer your question; those machines should work fine. You might want to try some other *buntu variants to checkout other desktops. You can easily install them after the fact, but if you aren't that familiar with GNU/Linux, downloading the premade image is more straight forward.
Oh, and the AMD just refers to 64bit architecture. If your cpu can handle 64bit, AMD is what you want assuming you want 64bit. I'd use 32 for a lowish ram machine, and Linux handles pae much better than Windows, so it isn't as restrictive as Windows is in that regard.