I tried to roll my own:
http://www.spmicro.com/mp3sidekick/

It worked, but not like the empeg... or even the Neo for that matter. I chose a DOS solution because it could be shut down simply by cutting the power. In the end, there was a compatibility problem with certain MP3s looping the last 2 seconds continuously. This was discovered after finally getting the sound card working in DOS. I never installed it in the car. I bought a Neo35 until my number in the Empeg queue came up. The rest is history.