'87 Speaker Wiring & Amplifier help

[Howaboutdat]

Update: I found out that I was wrong about the car having the premium sound option. So there is no factory amplifier.

With that, I'm still trying to figure out the wiring for the factory...

[Howaboutdat]

I'm trying to replace the original radio in my car ('87 325E). The replacement stereo I'm installing doesn't have a built-in amplifier, so I was planning to either install an external amp or if the car...