Before I picked up my Delta 1010, I asked the tech support people at M-Audio for their recommendations on processors and motherboards. They sent me an e-mail which identified specific brands and models of motherboards that had been tested and found compatible with the 1010. Unfortunately, I deleted it after I put my system together, so I can't relay it to you. But I'm sure they will give you the same list if you e-mail them.
What I can tell you from memory is that with a P4, they said that anything with the Intel 850 or 845 chipset should work with the 1010. I don't remember what they said about the P3, as I was not looking at that option. For AMD processors, they were only a couple of specific combinations that they recommended. I recall that they were pretty adamant that they had only found one mobo with a VIA chipset that they had tested that did not have compatibility problems with the 1010.
For what it's worth, I went with a P4 1.6 and an Asus P4TE, and I have had no problems. I know I probably could have saved $150 with a more budget-oriented AMD setup. But if I were looking to save $150 downgrading some part of my recording setup, it wouldn't be the mobo/cpu. I would just get way too frustrated if those components gave me any problem, and I'm not doing this for the frustration of it.
One other suggestion that you might consider in building your system is the Matrox dual-head video card. Folks on this board seem enamored with it, and for good reason --- for $50-$60, you can get a video card that lets you use two displays. Pretty handy.
Good luck.