Aeronaut: I tried the CTSSA001.2 adapter. I don't have an amplifier as I have the premium 70 sound system with only four speakers (two in the dash and two in the rear doors).
FredEST: I think you need the 20-280 adapter from incartec to connect to your amplifier. You'll also need the 29-694 adapter and the 29-005 lead to get the steering controls to work. Check the incartec site for details.