Hope I'm approaching this the right way.

I want to change my system to a MP3/ AAC ect. based (not cd, hard disk or usb) for a one Citroen Picasso. The existing crap cd player is linked to the dash board computer and also the audio control interface (don't know what its called) located at the steering wheel. I guess I could forego the extra audio interface, no biggie, so any recommendations especially from Picasso owners?