I figured out my audio-out question: The volume controls the analog audio out, but not the digital.
I'm using a 49TXi receiver. It detects what kind of digital audio signal it receives, and displays it: Prologic, THX Ultra, etc. This worked fine with the digital box, but with the HDTV box, every station from 2 to 7xx shows the same thing, Dolby PrologicII. Is the HDTV box not passing on the info, or has it all been converted to one format, or what?