I was curious again so I checked them out myself. Note they seem to specifically mention MP3s on CDRs/CDRWs only.

Kenwood DDX7015
(from website here)
Plays DVD-Video, DVD-R/RW, DVD+R/RW, VCD, CD, CD-R/RW and MP3/WMA-Encoded CD-R/RW Discs

Kenwood KVT-715DVD
(from website here)
Plays DVD-Video, DVD-R/RW, DVD+R/RW, VCD, CD, CD-R/RW and MP3/WMA-Encoded CD-R/RW Discs

Clarion VRX935VD
(from website here)
Plays MP3-Encoded CD-R/RW Discs
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Christian
#40104192 120Gb (no longer in my E36 M3, won't fit the E46 M3)