looking for a good, small, low power, portable board

[ron minnich]

Folks, I'm looking for a very small board with the following:
- x86_64, preferably with virtualization capability
- 4-8 G or so of memory
- intel e1000 or rtl8139 gige

- coreboot not required, but strongly desired
- serial port required
- graphics not required, and in fact discouraged, and if it's not
there I'm happy
- usb not required
- pcie slot desired, not required
- would be nice to have a case, but we can manage otherwise

if anybody has a suggestion please let me know.
We need several to run this: http://akaros.cs.berkeley.edu/akaros-web/news.php

A case would be nice.

thanks

ron