In the 1940's, we standardized on a INTERLACE, 480 line television standard because we did not have the technology to easially broadcast more data or even handle a progressive-video signal.
Even now with all our advances, transmitting OTA high-def signals has a lot of issues.
So you are not going to find a "VCR Rabbit" type system for your home to move HighDef signals (and DD 5.1 audio) to another room. It's just too much data.
Cant you just order another HD cable box and split your CATV feed and run coax to the second room? Thats about the best way I can think of.
Steve Did you just want to control the box from another room? In that case most niles and xantec systems will work. If you can get a learning remote to learn the signals, they should be in the normal range and easily bounced to another room. g