Maybe ill try removing the factory amp all together.
Run the fronts to the aftermarket head unit front.
Install some speakers in the sub location and run to aftermarket head unit rear.
Run an RCA from the sub out on aftermarket head unit to an amp and make an enclosure for a traditional 10" sub in the hatch area.
I already have a false bottom in the back to hide my nitrous. I can fit an amp there no problem.
I wonder if this would give me the clarity and bass separation I am looking for.