Q-man the changeover to digital has already taken place. It never-ever had anything to do with the cable companys. This change over was applicable to over-the-air broadcasts only. Some of the cable companies were using the publics mis-information to get thier analog customers over to digital. They weren't telling their customers that the analog signal that is supplied to them is and was not regulated by the federal mandate.
KAD he is paying for it.
Sounds like more ways than one. He already said he's got three boxes from comcast.
Q-man it appears your not going to be able to use your DVR the way you want to. It sounds like you want to use the channel switching provided by the DVR, so you can watch one program and record another. I believe the problem lies in the decoding by comcasts cable box, your DVR just can't do it. It's propietary stuff, comcast won't allow it. They want you to rent thier DVR. You can record only what comcast's box puts out, beit whatever channel you select.
Oh you could set up a system using an 'A'-'B' switch and a splitter, but you would need to two of thier boxes in the loop. You would have to split the signal before their box. If you really want to do this I can go into detial if you'd like.
A new DTV will not help your DVR decode the comcast signal.