I want to change my head unit on my 2003 A4 Saloon to a better one (with MP3 Cd support and bluetooth).

i want to adapt the wiring to ISO, I am about to order the facia adapter, radio keys and wiring adapter, however Im not sure which adapter to get.

I have the audi Concert system, single DIN head unit with radio / cd and a singel Din 6-disc changer in the glove box.

My standard speakers consist of door components front and back and a sub wooker on the parcel shelf.

how can i tell if im half amped or fully amped ? which adapter do I need to buy ? any suggestion sof the best / cheapest supplier ?

Thanks