I had a little time this afternoon, pulled the console to peek at the "sub", interesting.
Its a dual voice coil in a sealed enclosure.
Looks like a descent little stand alone amp in there. I am assuming they pipe full frequency from both channels to it from the deck, and then deal with the crossover on board.
I am going to replace the head unit pretty quick and may just bypass that all together, and try to find a "good" hiding spot for an amp and bass bin.
As far as the deck goes, I again assume with one of the din mountable units, adaptors are readilly available to fill any voids in the dash? Thanks, Bob