I have a Cassette player in my BMW as well as a CD changer. The Cassette player has spun maybe 1 or 2 tapes and thats it. I tried that cassette adapter hooked to my Ipod, it was terrible in sound. I then picked up a Griffen I-Trip tuner module. That sounded better than the cassette adapter, however was still weak. I have given up on that untill I can wire in a direct "Line In" input.
In the end, burned MP3 onto a CD as a .wav are about the best compromise however you still are only limited to about 17-18 songs on average, but can be played in any CD player. I was not asking for a separate MP3 player, rather a universal CD/MP3 player that plays CDs and MP3s in a windows file structure. I have Giga Quads ( at least 50 disks

) of MP3 disks that have 70-80 songs on them. If the player was a MP3 player, it could play those till the cows came home. A person could load 6 of those in the changer and it would be like 480 songs or 3.9 gb of MP3 storage.
How can that become an 8-Track? If anything its the way stock Audio should be moving. All the Hyudais and Kias have it, as do many other makers like Mazda..etc.