I think what you are trying to do is too ambitious. The AMI works brilliantly. You get a robust hard wired connection to the AMI which also charges the iPod. You can get a bluetooth adaptor for the AMI which I'm sure supports A2DP, but I have no experience of it. Does the iPhone prep actually send an A2DP output?I was thinking about adding AMI to my A5 but don't like reaching over to the glovebox. I was thinking about attaching a bluetooth radio via the AMI in the glovebox and using the Iphone prep in my armrest with my ipod touch to send a A2DP signal to the AMI.
I find it easy just to plug the iPod touch in the glovebox, and it sits there most of the time anyway.