System complete... and I'm very pleased with the end result which is more bass added to the stock 9 spkr MFT factory Ford system.
I added these components:
JL Audio 500 Watt amp
http://www.amazon.com/gp/product/B0081K3M5G/ref=oh_details_o01_s00_i00?ie=UTF8&psc=1
Remote Bass Control
http://www.amazon.com/gp/product/B000UVWFPM/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1
JL Audio W3 8" ported woofer box
http://www.amazon.com/gp/product/B001UDIGAC/ref=oh_details_o01_s00_i01?ie=UTF8&psc=1
Used this battery kit.. it is a true 4 gauge wire and very flexible.
Scoshe Revopak4
http://www.amazon.com/gp/product/B001U636NQ/ref=oh_details_o02_s00_i00?ie=UTF8&psc=1
Here is the connection to the batter terminal. The wire that will be exposed under the hood is actually covered in a braid for protection.
The cable going through the grommet / firewall... added an extra nylon washer and some silicon to seal up tight. This hole actually goes through a thin double wall and is located about 4" to the right of the steering linkage when in the engine compartment. ( toughest part of installation!! )
Here's the amp that is mounted to a 1/2" thick piece of plywood ( painted black ) that is secured to the vehicle. Battery cable comes in from the driver side, ground is secured right to the vehicle frame near the amp ( make sure you scrape off the paint to get a good ground ), low level signal and remote turn on come in from the head unit, run down the center console and into the amp.
Here's the sub box just sitting in the back behind the third row on drivers side keeping my steel toed shoes company. ;-) Spkr wire was ran down the drivers side of the vehicle.
And my first song to test the bass was something a little old school. Yello... Gold Rush...
I have the gains on the input to the amp at about 50%, Crossover @ 120 Hz, and I have a lot of control with the remote bass knob on the JL Amp. On the headunit I have the bass clicked down two notches to keep the front speakers from "blapping" ... mid range down one notch, and treble up a couple. Front imaging sounds really good even with the stock speakers. Staging is nice with the center channel.. Ford did that part right.
As for the rear door speakers and 3rd row... they are what they are.. just barely "fill-in" if that. If you really wanted to improve sound in the back, you would pretty much have to go with some type of enclosed speaker I believe. Anyone remember the old Radio Shack Optimus 7 speakers?! Something like that mounted in the back is what I'm talking about.
None the less.. I'm gonna keep things the way they are for now and enjoy the bass!