I read that the signal is not the typical RCA jack hook up but has Data sent from the head unit to the amp and the amp processes the signal. Also that it sends data in HI, Mid, and Low Hz. So getting a full range takes some work. Guy on the other forum was talking about it. He put 2 of these subs in his truck under the back seat.
HERE is from the thread:
Heres the deal with the factory amp: I have the NAV, so it could be different without it, but idk. Anyhow, information is sent from the stock head unit to the factory amp but unlike an aftermarket HU and Amp which uses RCAs to send the signal to the amp, the factory HU sends DATA to the factory amp, so you have to bypass it with a signal summing device (because the outputs on the factory amp are high, mid, and low, NOT full range) then from the signal summing device(which turns the 3 way signal into full range) it goes into the Digital sound processor which takes out the factory EQ settings and gives you RCAs and a remote turn on lead to send to an aftermarket amp. I dont think a PDX would fit in the stock amps position anyhow. The stock amp is probably 6 or 7 inches across and 10-12 inches long, but as I said before, its like a data processor and there are 3 wiring harnesses that come off of the factory amp with LOTS of wires. we arent talkin about 10 wires per harness either. way more than that.
Ill work on the specs for the sub box. its wierd tho and even if you replace the factory woofer with a JL or other brand, idk how stable the factory sub amp is. from what I could gather, all the factory door speakers are 8 ohm so Im assuming the factory sub is, too. If you put a 2 or 4 ohm sub in there with an amp thats only 8 ohm stable, you're gonna burn it up. it would be the same if I had a 2 ohm stable amp and wired my speakers @ 1.5 ohms. its gonna burn it up.