HU Re-install on 88 E30 - aka fixing last owners mess

[r3zon8]

Started my own thread as a mental note/google reminder on the steps I took to figure out what the hell the last owner did to install an aftermarket HU and ultimately install my own new HU.

Im completely new(took delivery on 11/25/15) to E30s so please bear with me. I will try to answer my own questions as I learn and go along but feel free to chime in anytime.

What I know:
-Its an '88 325i/is
-Has fader control on dash; fader harness was cut and all wires taped, zip tied and no longer in use
-All speakers have been replaced with what appears to be RockfordFosgate 5.25 components(tweeter+id) up front and 5.25" rears.
-New wiring was run for new speakers

[r3zon8]

Fader Harness cut and taped off:
[ATTACH]102728[/ATTACH]

Q- 4 pairs; Are these the 4 pairs that went/go to all speakers?
A- These wires should be feeding the amp-IN but colors dont match up yet. I need to follow the wires further into dash as per Lukes writeup.
[ATTACH]102727[/ATTACH]

Q- Found this box in trunk near antenna assembly-is it the amp?
A--No, this was not the amp. Amp is MIA.
[ATTACH]102729[/ATTACH]

Found what looks like the AMP wiring loom. The amp itself is gone and the harness was cut. Wires were taped off and zip tied behind the liner.

[r3zon8]

reserved for pics