I'm thinking of doing something similar.
I've got a new 2010 Edge with the standard audio system and, of course, SYNC.
I'm already weary of the head unit - looking for a good navigation system and, if possible and not too much more, to keep the SYNC.
I've been looking hard at the Alpine INA-W900 system along with this to retain sync:
http://www.sonicelectronix.com/item_14328_Axxess+AFSI-01.html
Any comments, suggestions would be welcome.
I don't really want to keep the SYNC because I can always call the 800 number for SYNC's Services, and the H.U. has all of the bluetooth hands-free calling, but I know my wife will be upset if I tell her that the SYNC's 911-assist feature will be removed. Maybe the $130 to keep the SYNC is worth it :-)
Any comments about the Alpine and/or SYNC retention?
Scott