From the boards you listed, the little Valley board is superior in terms of computing ability and minimal power draw.
As far as what else you need, I suggest thoroughly reading the FAQs.
Here are some resources to helpkick-start your research:
http://www.mp3car.com/vbulletin/advfaq.php
http://www.mp3car.com/vbulletin/forumdisplay.php?f=106
http://www.mp3car.com/wiki/