Hi,
If I understand you correctly, you have a working installation with one firmware, and you need to understand the configuration settings so that you can set up another installation using newer firmware. Correct?
There is a file on the DMS called "phatbox.ini" which has options for all models. As you have found, the issue is to establish which is approriate for your head units.
Some related info is here...
http://forum.phathack.com/cgi-bin/yabb2/YaBB.pl?num=1134412272/0#15Read the posts just before this as well. They make the suggestions ono how to identify the letter used by temporarily modifying the phatbox.ini file (be sure to take backups). I think that in combination these techniques may may help you.
If I misunderstood the request then you'll get better info if an Audi owner chips in...
Good luck!