I have a different perspective on the CD changer issue. I should have elaborated on my previous post. I am "intrigued" becuase I like electronic projects that are a challenge.
I am quite happy with the sound quality of the empeg and have only the "fun" desire to do such a project. I even have a second head unit that lets me use CD changer and radio. I have used the CD changer for long trips when a few friends will bring music they like with us and I'm happy I have it. Other than that I only use the CD changer when I forget my empeg which this project would not help.

There is also the issue of car audio competitions (which I don't participate). They only allow CD's (for what I think is a good reason). This accounts for a very very small percentage of users but is often great advertising for companies which is why they probably sponsor. I would love to see an empeg head unit in the winning car at an IASCA competition even if it didn't use MP3 music.

I have heard all the reasons why a project like this should not be done and I agree with most. However I think this shows that the empeg can be integrated into other components and control just about anything.

I certainly didn't want to imply that the designers at rio/empeg take time to do this I just thought there was enough great programmers in our forum that could handle such a simple interface. (about five serial output commands and a screen output, I think some of this has been done before)

I had originally thought that an Alpine CD changer would be good because I could go ahead and decode the bus myself with mine but I found a website that has a forum of people that have done some fantastic work reverse engineering the Sony Unilink bus. They don't have it 100% decoded yet but there is enough info to control a single CD changer.
The site is http://www.cus.org.uk/~cleggy/resources.htm

Alex Lear