Thats interesting, never knew that one
Lots of people have put inline adapters on their rear speakers to add Bass Amps to go with their stock setup, or you can if you are gonna go the aftermarket headunit route, you can add amps for the speakers and a bass amp as well.
Its fairly easy, you just need to run a 4ga power wire from the battery to the trunk to your amps and then run new speaker wiring to the speaker locations in your car, ie the Doors and rear deck and then hook up the amps via RCA cables to the HU, you will bypass any factory installed amp at this point. So it won't matter if that amp is bad.
I hope that helps more? (More so than my last post)
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