Was just reading thru my legacy06 manual and leraned that it had a option for an extra CD Changer. The 4-way switch on my audio unit had a label "CHNR" apart from TAPE, CD & BAND. That was, according to my manual, were i would access the extra CD Changer once fitted. Can I fit aftermarket CD changer (MP3 readable). The agency guys don't seem to know much about it. How come no one has mentioned about this?