I'm not exactly sure how this works, but there is the CD-RB20 which adds RCA in, with IP-Bus pass-through. I have a CD-RB10 which is RCA only, no IP-Bus, and it works well. You may want to contact Pioneer to see how exactly it works. Does it select which ever signal is "on", or does it only function for the CD changers. Just a little help for ya!

BTW, don't cross post!

edit: Google turned up this place which sells them, and mentions that "provides RCA preamp inputs as well as another IP-Bus connector for a CD changer or other IP-Bus peripheral." Which makes me think you should have no problem with it!