Regarding using the Tivo as a Rio-like audio player, here's my analysis from last March:

http://sourceforge.net/forum/forum.php?thread_id=653185&forum_id=110068

Summary: it'd be of little use for hosting audio, but could be a streaming client using mpeg-2 or lightweight codecs.

Somebody may have already done this, but I haven't looked into it.

Reed http://jreceiver.sourceforge.net