I should have mentioned that what I do is take those mp3's and put them on my Garmin Nuvi 660. It transmits over the radio, plays mp3's, answers my phone calls(while automatically pausing ant mp3 currently playing) and gives directions (also pausing the file player).

All I do is dump them on an SD card and put it in. The media player finds them. I do have to edit the meta tags to get stuff to sort the way I want. I use MP3TAG. Free (though I made a donation).