hi there, i have jus brought an audi a3 1.8 T on a S plate.i was pleased to see that it has 4 bose speakers,but apparently there are powered by an amp in the car which i cannot find? Also since i have put in my old pioneer head unit in the two rear speaker channels coming from the audi are not workin but they were before.the sub is also not workin and i am not sure if it was working before. i wired the connector plug to my wires from the head unit and plugged it into the cars plug..(no rear speakers)the rear speaker wires coming from the head unit work when i put them into the front speaker connection...so all the front and back wires from the headunit are working but i still have no rear speakers?or sub,so iam guessing its the rear channel but from inside the audi? so 1; is the standard sub worth keeping? 2;I have a pioneer sub i may install,can i run it from the audi amp?if so where is it lol!? 3: why have the rear speakers(and possibly sub) stopped working? 4: Can i comfortably fit 17inch wheels to standard suspension? can vw wheels go on? thank u for ur time ..i hope u can solve my frustraitng headache!