Adding Amps to Factory System without a LOC
I have an 06 bmw 325i and I want to add a 4 channel amp for mids/highs and a separate amp for my sub. I basically want to avoid using a LOC because the only speaker-level source comes from the factory amp that induces heavy equalization and limited range per channel. The factory radio uses twisted pair (balanced differential) low-level outputs to the factory amp and my question is how do I properly source those. I know it would be easier to just add an aftermarket HU but I would lose way too much function going that route.
Refs: damonhargroves, mazzasec, na rsx, mistergrubbs, mike465, astrolade, rival904