I've spent the past 4 hours searching all over the Web. It is very likely that the CD changer in the glove box is a Pioneer unit that is controlled via their (I)P-Bus interconnect. And they sell a "cheap" ($50-$80) box (CD-RB20) that can "pass through" the P-Bus and add two RCA input connectors. From some terse comments I found it looks like the audio is really bused together - If you can't find a way to make the CD changed power down or shut up the two sources get mixed together. Normally the Pioneer in-dash head units will allow you to select the Aux input and (presumably) tell the changer to get off the line. So that gives me my audio feed.

For control there is the Kenwood wheel-mounted IR remote or (if I can get a tuner module) the Sony wired remote. If I have to mount the empeg too far away I can lengthen the Sony's harness or extend the Kenwood's IR with some fiber optic light pipe.

So maybe I'll mount it under the seat ;-)