Looking to feed internet radio from my laptop into the Safari's sound system, I read posts where folks added a Sony XA-300 (has USB input) to their Sony CD player, gaining additional audio inputs. For those of you with Airstream's Audio/Video upgrade package, you probably have an XA-300 already.
I found the XA-300 buried behind the access panel to the Sony headunit. For some reason, Airstream decided to not bring out the USB jack. I plugged a standard USB cable into the XA-300 and ran it out the same hole as the CD changer cable. My laptop immediately recognized it as "USB Speakers" and all I had to do is select the source on the headunit as CDC4=USB.
btw, if you've not listened to Pandora, it is worth a look. You create you own "radio stations". By asking you to seed the station with a song or artist, Pandora helps you figure out what type music you like and then keeps streaming great songs.
Pandora Radio - Listen to Free Internet Radio, Find New Music