msi and gigabyte are recommended by tomshardware on 865 and 875 chipset.
but yr 2.0g P4 is not the 800Mhz FSB version, I don't think u need those dual channel boards. For atx, u can consider via P4X400 chipset, I have the P4PB-FL, very stable, just u cannot use all three ram slot to host DDR3200, only the 2nd and 3rd slot works. Besides, for ddr 400, they recommend cosair memory, I tried a generic one, failed. I put two sticks of HyperX 3000 in it and running at ddr400 2-2-2-6, no problem at all. If u do want to get this one, the ultra version cost less than $80 and comes with flash card readers, really a sound deal.
About OC, I tried a Celeron, it does not go through but I read some review said their 1.8a go straight to 2.7g. I will definitely try that later.
Besides these big atx, u might consider shuttle's miniQ of 865PE board, too ---- if ur modem is pci. >$320 in that case.