Actually, you could also get one of these:
http://cgi.ebay.com/ws/eBayISAPI.dll...746071592&rd=1
It's also got a built in TV tuner. I've got one and it works pretty good, though I don't have it set up the same way you would.
You would plug it into your VGA port on the mobo, plug your touchscreen into the unit's VGA output, and plug the composite screens into the RCA outs.
Oh, and for $10 more you can get the one that has a built-in video recorder.
http://cgi.ebay.com/ws/eBayISAPI.dll...739126477&rd=1