I started building my 2014 F150 Tremor 2WD about 4 years ago, started with suspension and then moving into the stereo. Basic system at first, stock Sync 2 with factory speakers and a basic amp with a sub. MEH
I used to work at Streamline Audio in the 90's where we built the Gates Bronco, I was sponsored by MTX and competed in the Expert class with my 91 Caprice Classic in Dallas in 1996 but hadn't done any decent stereo for years. My kids are in their 20's and I wanted to build something equal to the demo vehicles here in Phoenix/Tempe back in the day. Down side is I'm not physically interested in doing it so I farmed it out, both good and bad choice on that.
I went with 4 JL 13TW5V2-2 subs on RF T1000bdcp amps in a blow through, my direction was cut the cab and flush mount the subs, unfortunately I got blind sided with the installer not following that and building a horrible 4th order causing quite a bit of bass issues but I lived with it for a couple of years.
The top end is Audiofrog GB6/2/1 in the doors and GB 6/1 on passive crossover as center in the dash, I chose the JBL MS8 processor as it was still considered one of the best sounding ones out there and I ran the top end on 2xT400-4 RF amps. I designed and built some 3D printed pods in the sail panels along with some custom dash panels for the center channel and 6.5" subs. Replaced the electronic locking diff switch with boost gauge as I have an Eaton trutrac in it now and right side cigarette lighter with volt meter and custom built some circuit boards to allow me to run a 17 Raptor steering wheel with paddle shifters.
I upgraded the stock Sync2 to Sync 3 and I've been decently happy for awhile, I could only run 2 of the 13's at a time because 4 of them overwhelmed the port/front chamber.
I hit up a buddy of mine Dennis Barnes, one of the lead guys on the Gates Bronco design iteration 1 and 2 at Streamline and then directly for Alma at her shop and we decided on doing 16 of his 6.5" subs he just had made in two 6th order enclosures. Initially we paralleled each set of 4 drivers to 1 ohm then series to 2 ohm but with box rise were seeing 4.7ohms to the amp and under 500W output. We're now at .5ohm to the amp and seeing 1.3 ohms and 13XX watts output but unfortunately the original installer ran individual 6ga wiring with maxi blade fuses making 120A max which the amp easily blows through (literally).
Next steps is to do the following:
1. Replace 2xT1000 with 1 T2500 RF amp, replace front to back wiring with 1/0 and install a 600A fuse up front for any shorts. Replace front AGM battery with 12 35ah LTO cells in the bed and upgrade to 250A large case Brand X alternator, that's all ordered and on it's way.
2. Replace 2xT400-4 with 2xT1000-4 amps and add a 2nd T2500 amp and redo the rear amp rack and covers.
3. Big steps here, custom door panels with leather and custom dash, full old school interior swap like the old demo vehicles including seat swap.

Some photo folders:
6.5" subs enclosure and install - https://photos.app.goo.gl/yN968BfoeQ2cyqfS8
Exterior pictures of the truck - https://photos.app.goo.gl/xH6ZjTyLVMXfjSxi8
Original audio build - https://photos.app.goo.gl/4eBLUfhgfmaEAfD89

It's a fun build that will be probably ever ongoing but I own the truck outright so it makes it something to keep my brain busy.