Mike, the audio could also be carried via digital coax (single ended RCA type) as long as your receiver is capable of processing it. And if you really get fancy and have a processor that switches video as well, you could run one HDMI cable from each component (dvd, tivo, whatever) to your processor, and one HDMI cable to the display. That would handle both HD video and multiple discreet audio channels (surround) with a minimum number of cables.
For whatever reasons, most Directv HD boxes will disable component, svideo and other outputs as soon as you plug in an HDMI cable, so if someone was thinking of boosting an output through a modulator to watch it on other sets, you would have to keep that in mind.
I like your idea of a different box at each location. Do you run 4 coaxes down from the dish to a multiswitch in the back of the bus to where the distribution originally was? Are you lucky enough to have two coaxes to each location to use dual tuner tivos ?
Also, how do you get more than two weeks out of a TIVO without hooking up to a regular telephone line to get the programming signal ack'd ?
I have not had time to dig too far into AV stuff in my bus, as I am taking care of more pressing issues first, but it is on the list for sure!
Sounds like you have a nice setup for sure!
What size is you salon display?