I just finished my upgrade path of adding an amp, subwoofer, and front dash speakers. I wanted to add some thoughts the journey in case it helps others. My upgrades were on a 2019 Laramie with the Alpine 12" Uconnect.
I started by upgrading my factory front and center speakers. This is an incredibly easy install, and assuming you get the speaker adapters, probably take less than an hour. I used the Kicker 46CSC354 3.5's, which I'm very happy with after adjusting the EQ a bit.
Next, I began planning an upgrade the stock subwoofer, thinking I could just replace the driver. Once pulling the sub, it became pretty obvious this would not be ideal. The box is tiny, the sub irregularly sized (between an 8" and a 10" from a mounting perspective), and has an unusual voice coil arrangement (3 voice coils). Even if you added a spacer and shallow mount replacement sub, you would still be getting less power than the factory sub. So, I decided against this option.
I looked at pulling the factory sub, and adding one under the rear seat. I built a box similar to those described in other threads (picture attached), and added a relatively shallow 10". I generally prefer ported, however, there is just so little room, that I ended up sealed. This arrangement is working pretty well, but the seat does rattle when I crank it. In hindsight, I would have made the box slightly shorter to allow more air gap between the sub and seat.
Next, I mounted my amp in the factory sub location. This seems to work pretty well, and there is some airflow with the holes in the carpet panel for the factory subwoofer. At first, I used the factory subwoofer high-level feed to get signal to my amp. This worked, however there were a few downsides: 1) The active noise cancellation (ANC) caused a fairly loud, distracting tone when it activated, 2) there was some noticeable turn-off thump from my amp (Alpine MRV-M500), and 3) the signal to the factory sub seems to be EQ'd by the amp (was not a huge deal for me).
Since I'm cheap, I de-pinned the ANC microphones to fix the distracting tone when ECO engaged. This fixed the tone from the sub, but replaced it with another issue. That issue being the noticeable drone when the truck goes into ECO mode. Generally, this drone was tolerable, but there were occasions where it became annoying when accelerating in ECO mode. I decided this was a deal breaker.
Finally, I decided I need to just pony up the cash for the PAC Amppro (AP4-CH41). I was able to find it for less than $200 shipped online. The install was fairly straightforward, and as a nice bonus, it provides a remote turn-on for your amp which fixed my turn-off thump issues. I then put back the ANC, which still functions through the factory 6x9's. It may not be quite as effective without the factory sub, but is way better than no ANC (ECO drone is now hard to detect).
Hopefully this helps those with their upgrade planning.
