I want to replace the radio head unit in my non navigation 2006 S-type fitted with the Premium Sound system with a Double DIN Kenwood BT head unit. Looking at the wiring diagram, it looks like I will need to fabricate a speaker wire loom to go from the new head unit to the rear that will have to be cut in to the output wiring of the power amp. If I want to keep the rear subs I'm going to need a new power amp as well.
Are there any other options available like a D2B fiber adapter that will take the audio from the new head unit and mux it onto the D2B fiber connection to the existing power amp. Google searches don't bring anything up.

 

couple of things , there is speaker wiring to the back doors. you could splice in to those at the B pillars then run them to the amp loom witch then runs to the parcil tray .
also you have the option of adding blue tooth through the existing head unit via d2b here .

http://veffremovve.wixsite.com/jaguar?from=%2540

witch is what I've done . i also upgraded the speakers and parcel tray subs and added a
high level to low level rca converter
( RCA CAR Audio Line Level Converter Output HI LOW Level | eBay )

to the amp sub out puts to run a separate amp and a boxed 12" sub in the boot. it sounds brilliant !! almost as good as my other car with a competition pioneer stereo that has the full on kit 3 amps , two subs 4 6x9s , front components , power acoustic 4v pre amp splitter/booster 13ch graphic eq . and a massive capacitor . sure the pioneer is louder but not by much and they are as clear as each other . so there really is nothing wrong with the factory alpine setup . with the appropriate add ons !