Just sticking to the two choices you mention/linked, it would be hands down; go for the AK31 & XP1800+. Just plan on getting a sound card (if you don't already have one) as the onboard sound is spotty at best. There are of course, other combos out there but that one seems to be pretty good.
EDIT:After looking more closely at that AK31 combo you linked to, I found a couple of things decidedly wrong with it. In looking at the board that is offered, it is the AK31, not the AK31A; which is a big difference. The details on the MB list the chipset as the KT266, not the KT266A. Not such a good deal now. You'd be better off getting the same (Better) combo from NewEgg for around $140 (plus tax) shipped. That would be the AK31A rev. 3.1 and an XP 1700+ CPU.
Another solid option that would be within $20 or so of the above suggestion, would the the the SL-75DRV4 (Purple Ray Ver.) with an XP 1700+ CPU; also from NewEgg, ordered separately.