Stereo Sub Speaker

[B134Davidson]

Hi peoples, I have a UZZ31 Limited. It was not optioned with the rear sub speaker, instead it had some air purification unit mounted under the back parcel shelf. That came out relatively easy and found an even easier fit into the jumbo bin. I've had a nice 10" sub mounted in the existing hole. What I need to know before I pull the whole interior of the car out is:

Would anyone be able to tell me if the factory amp and wiring for the sub be in place even though it was not optioned?

It has the EMV screen with surround sound option but no sub level adjustments.

If the wiring and amp are non existant, where would I find the amps that power the existing rear speakers?

Would I be able to take a signal feed from both L/R channels to a two channel bridgable amp to drive my sub?

I had the CD stacker out and found an electronic box with millions of wires going to it, but no description as to what it was.

I found the tuner unit hidden under the rear seat when I fitted band expanders to both the aerials, there exists two more boxes with a spagetti of wiring attached. I assume one is the radio tuner and the other the worthless NTSC Tv tuner.

I would appreciate help on this as the stereo sound doesn't do the car justice. Although I have an awesome sound coming from the rear exhaust anyway.

Want a throaty sound that burbbles "grunt" no matter what revs your pulling.

I'll fill you in. :o :o :o :o ;)