Well you have a bigger question before you go out and buy a motherboard - which chip (AMD/Intel). This is important to know.

After a little research, I ended up with the AMD 1.4GHZ T-bird (over the Pentium IV 1.7GHZ) with the integrated motherboard. Some down sides to it, but overall a good fast system. You pick up speed on the AMD1.4 vs. the P4-1.7 but you get some extra heat. Compatibility isn't even an issue these days, but have not had a problem.