Maybe the setup isn't entirely odd. They may have made the (not unusual) assumption that you don't want the home theater sound going into the whole house, so it's setup to have HT in one area, and music in another. Typically the whole house source would be setup to be used in the TV area as well.
Are you sure there isn't any wire running from the whole house closet to the TV closet that might be intended to be the whole house audio source? IF there is, you could hook it up to run the source either way.
And are you sure you can't run some wire in an attic, basement, air duct, etc?
The other major wireless music source is the Squeezebox Duet, but that's and the Sonos are really about much more than what you need.