Symphony vs Symphony II - what's the difference?

biggest difference is the built-in 6-disc changer in the headunit in the Sym II
 

<ul><li><a href="http://www.ibiblio.org/tkan/audi/radios/radios.html">...you can see more info here...</a></li></ul>

..and don't forget about the lack of "Hidden Equalizer" in the Concert II.

Oh yeah...forgot about that one...
 

I had used the hidden EQ settings in my previous car 2001 2.7T, but when I got the 4.2, the Symphony II headunit did not last long...just long enough for me to ride from the used car dealer in Chicago to Scott's house a few miles away, and voila! RNS-E in place of the Symphony II headunit.

The one thing I did like about the Symphony II, however, was a display of the volume bar which is noticeably absent from the Symphony I and the RNS-E.

wiring is slightly different too. See some of my docs on www.nsxjr.com
 

...depends on what you are trying to install etc.