I have a Kenwood MP3 player Hu in my Si - I just keep a few CD's full of MP3s handy. But in the S I wanted to keep the stock HU/controls and not add any wiring. So I bought a Belkin Tunecast and I just use my iPaq with a 512MB SD card as my MP3 player. Considering the S isn't usually a long distance driver for me - I have plenty of music to listen to and no wires...