I have a Series 1 Unsub Tivo. I just got an HD TV. Since I own the Tivo, I wanted to possibly save the rental from Comcast of an HD DVR box, and use the Tivo to record non-HD TV shows, and just change my Comcast box to an HD box without DVR. Will the Tivo be able to pass through the HD signal for viewing on the TV, or can I NOT use my Series 1 Tivo at all in the "chain"? If this is the case, than my only option would seem to be to get from Comcast the HD DVR (assuming it is probably a 6412).