the 64 model is a lot better than the xp. amd made some major revisions to the processor architecture. in my opinion, 50-100 bucks would be worth the jump to the athlon 64 3000+.
I know a lot of people that are planning to purchase a AMD-64 (including myself). But if I don't have a 64-bit OS to run it on, then it's really a waste of money.
One of these day I will seem myself with a AMD 64-FX cpu, but I would like to be able to technology, as appose to just showing it off.