I burn with Adaptec 4. I have a S&F CD-R/RW that burns at 6x. I never get buffer underruns nor does the skipping happen in the wifes Jeep.
I do notice that only a few CD-R work. I have had great success with Memorex. Maxell is ok too, but kodak and some others do not work in the car.
Do you know if the Aiwa CDC-MP3 is any good? It looks like it plays MP3's.
Also..I have been thinking of making my own MP3 changer. I have some old parts from PC's and Laptops that I was going to put together. Did anyone out there try that? I see sites on the Net that talk about it but just was wonder if anyone had some feedback.