Anyone know how to get one of those changers with an external controller to provide straight line level output via a pair of RCAs, which could be plugged into the Aux channel of the Riocar?

Sorry, didn't have a reply earlier...

SONY make at least one model of CD changer with RCA line-out connections and a WIRED remote with LCD. You can use this with any head unit (including the empeg) that supports line-in. The wired remote head is pretty thin and easily mounted on your dash, armrest, etc. A friend has one in his minivan and I just remembered about it today (mainly because I was just in the vehicle 5 minutes ago :)

Bruno