Yes, the barton is the better chip.
Are you interested in OCing at all? Of the people who have tried OCing the xp2500, 92% have been able to run them @ 3200 speeds. When you consider that some of them had boards that only support 333 fsb, and people who were trying for the first time, that is an impresive number.
Try reading a little in the OCers forum, before you try or buy. If you have any questions, please ask.
My AV8 3rd eye would be just fine with your ide drives, and that gfx card.
You should also know that a A64 3200 is easily 15% faster than an xp3200. Since the A64 is less money usually than the xp, the board isn't that much more of a cost. It would allow some upgrade path, but realisticly, you would be in the same boat in a couple or three years.