If your Sony Changer works with the Harmony via an adaptor then it should work with the Symphony using a different adaptor. See:
http://www.connects2.com/c2search.as...=226&modID=547
as far as I can see you need this:
CTARVS009 Connects 2 CD Adapter - Sony
Rover 75
Alpine
XQD101043PUY Symphony High Line (ISO Block)
hth
Mike