I have Charter Cable, Greenville SC. I enjoy the music channels playing in the background. Is there a receiver, either cable-box or QAM-64 (they are in-the-clear here, at least for now) that will receive the audio and not require my TV video be on?

not sure if i'm answering your question but just about any av receiver will accept your cable box input and be able to play it on external speakers as long as it's fed in from cable----> receiver ----> tv. you don't have to have your tv on.