FreeNAS would make an excellent media server. I'd love to try it out, but I don't have the cash to invest in things i would need for the system right now.
It is really cool how it works. You have a box without a hard drive. Then you use a USB to boot the OS, and a hard drive enclosure with however many hard drives. Then FreeNAS becomes a share point for all clients on your network.If you got an enclosure with 3 or 4 hard drive slots that was RAID compatible you'd be able to have an amazing media server.
I am just learning about how it works so I can't go int oa lot of detail. Check out the FreeNAS build video series these guys made. Very good information.
And check out the FreeNAS website.