My choice is the Asus a7n266-VM (AA - AMD ASSURED).
I think it should support a Barton 2500+, but I'm not positive.
The board is not overclockable, but has everything integrated including 5.1 sound. I suggest you look for refurbs. Asus made the power/hdd led/reset switch/ things all goofy on the board. Many people RMA'ed because of this problem. If you are lucky, you will get a brand new board for a discount because people couldnt plug in their power buttons and stuff.
I really like my board. Small, integrated, VERY FAST, and cheap. IF they made it overclockable, I would probably give up my raid mobo for this cheap asus. But so far, the only way to overclock is via software (which I have yet to find).
Let me know if you find out for sure if it supports a faster chip. I have a 1700+ pally in mine right now, I might be looking for an upgrade soon.