Hi there. I have an Audi A3 2002 mod 8L and want to upgrade my soundsystem. I have an aftermarket headunit wich I will put in my car soon, when I get the interface I need in the mail. But I've heard that there is an amplifier in the back that amps the to speakers in the rear? Is it possible to wire 6x9 to the amp? I have the normal Audi Concert system, not the bose version.