Tom's didn't like the Abit IS7, but Anandtech loved it. I've spoken with several owners and they mostly loved theirs as well. As for the IC7, it cost more and has fewer features than the IS7.
Serveral owners of the Epox board have recommended them.
As for your system combos:
The K8N Neo Platinum and A64 3200+ sounds like a great combo.
I already talked about the P4 platform, for more information on the voltage issue read my review at <A HREF="http://www.sysopt.com" target="_new">http://www.sysopt.com</A>
On the "low end", I'd go with with an Abit NF7-S (actually a high end board) and the Mobile XP2500+, then I'd overclock the CPU to 2200MHz (200x11) for XP3200+ performance.
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