We'll only turn on the XM receiver when we are using the motorhome, but the radio also has an AUX IN, which we plan to plug our little Rio into (I just received my 2GB SD chip today.) It'll play CDs also (with MP3/WMA support), but this is much easier.
I saw one or two radios that have a card slot for SD chips to plug right into. Wouldn't that be nice to have on all the radios....