Got tired of not having bass control. Went ahead and experimented with a fix today and ended up adding an amplifier to the stock sub. Thought about redoing the whole sub enclosure, but those days are over for me. I'll share some discoveries.
The wiring harness has 4 wires. All wires go to 1 6inch woofer. The 12v battery is right next to the sub under the plastic enclosure. There's even a chassis ground with a bolt in the area.
The woofer is a dual voice coil. Each VC is 8ohm and wired in parallel. For one channel its blue/violet (-) and white (+), for the other channel brown/blue is (+) and brown/white (-).
Anyway, I just used ONE of the pairs of leads for the input to the amp, and ONE pair of leads to the sub and this worked perfectly. I have experience with being too risky with OEM electronics,and these systems are not as tolerant of mistakes as aftermarket stuff.
Result: The sub works great now and I have a bass knob to adjust bass as I see fit. This also balances the system more makes it overall way more enjoyable.