Maybe you could get along with the main TV getting HD and the 2nd TV only getting SD. If the receiver is near the main TV and you can get and HDMI cable there then you can use the 3 RCA outputs to a coax converter (cheap) and plug that into your Video Control Center.
The other option is to bring a 2nd input in from the antenna, and run that to the bedroom (either new run or use the coax that already runs to it) and place a 2nd receiver at the 2nd TV. Now you have HD at both locations AND you can watch/record 2 different channels at the same time.
