Here is one option that has been benchmarked to over 100MB/s and is very inexpensive at about $600 diskless. Dual NICs, USB 3.0, etc.:
http://www.smallnetbuilder.com/nas/nas-reviews/31769-thecus-n4800-nas-serve...
I would suggest going that way first, and if for some reason it doesn't work out performance-wise, then look for a video-bandwidth-optimized NAS or server.
Alex (
DV411)