Unfortunately, not too much out there looks like the stock units, except other Beckers
http://www.beckerelectronics.com , some Nakamichi units, and a few Pioneers. Usually these are pretty expensive, and I hear the Nakamichis have some CD/reliability problems. The only unit I have seen recently that does the MP3/CD/CDR/CDRW/WMF combination, doesn't look TOO tacky, and is under $300 is the Blaupunkt MP3000.
http://www.crutchfield.com/cgi-bin/S-3slJrImwvtd/ProdView.asp?s=0&c=3&g=62700&I=023MP3000&o=m&a=0 It is about $179 at Costco in our area (but different Costcos seem to carry different goods! - May not be in your area).
If I am not mistaken, your factory head unit has seperate amplifiers for some of the speakers. Wiring may require a search of past threads and some further posting on your part.
__________________
John
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E