Interesting about the RNS-d. I'm not aware of any difference in the Bose amp between RNS and Symphony. There is definitely something weird though with how Audi do the preouts and turn on/off of the amp though as changing either component for aftermarket has yielded odd results in my experience, hence why I have thrown out all of the original kit from my Murple and done aftermarket everything.
Once I have the Murple up and running it will be very easy to swap out aftermarket head units so I'd be happy to give yours a try and see how it behaves
