Hi, I am installing a new Android Head unit.
The head unit will be hooked up to an amp (via RCA cables) to power the door speakers (up-rated door speakers) and a subwoofer.

So essentially, I would like to use the existing car wiring which feeds the speakers, the only thing I want to do is tap into them and hook them up to my amp.

I need to power my android headunit, so would you also be able to tell me which is the Pos and Neg (Ground) in which connector which fed the widescreen satnav bmw original headunit? I also will need a switched power feed and a illumination feed (so that when I turn my head lights on, the android headunit buttons light up).