I use an ASUS C60M1-I for my FreeNAS install which works great. The only problem was I had no easy way to monitor the CPU temperature which is a bit concerning since this is a fan-less motherboard. I came across the mbmon package though which does everything needed. Here is the quick way to install it on FreeNAS 8 on a USB Drive:
mount -uw / && pkg_add -r mbmon
After that log out and back in and you should be able to temperature and voltage info by executing the mbmon command.