Not exactly, as the two can work side by side but if you are playing mp3's then why go back to cd's.
Have a look at this
http://www.phoenix-pcs.co.uk/acatalog/P ... ICX1R.html
Fitted it a Zed
http://www.350z-uk.com/gallery/displayi ... at=0&pos=4
The car is a UK car and they changed the head unit only, running through the Bose amps and speakers.
This gives you sat nav, dvd, mp3, mp4, Ipod, all for £980. if i had my time again that is the way to go.