Ok, one final post and this one is important if you're thinking of doing any sort of OE system upgrades.
So, while my system has been up and running for a year or so now, my son has had the car at school, and I only got it back this summer. One of the final "glitches" I've been trying to track down was why only the front door speakers were working. The rear door speakers worked, but were REALLY low in comparison to the front. Then, the center channel and two rear pillar speakers weren't making any noise at all.
After checking, rechecking and then triple checking the polarity of every single speaker wire, re-flashing every module associated with the entertainment system, I finally figured it out.
When I originally purchased all the different parts and pieces....before I discovered the touchscreen I was trying to use was faulty, I had a meridian amp installed in the system. Based off PowerfulUK's video I thought everything was forward and backward compatible. At that time, I attempted to flash the amp firmware load and it failed. (This was due to the faulty touchscreen, but I didn't know it at that time.). Anyway, I pulled the HK Logic 7 amp out of my 2012, and installed it into this system and got sound again cause I had crashed the Meridian amp. Thankfully, I was able to re-flash the Meridian amp in my 2012, because the TS wasn't faulty.
Anyway, long story even longer, when I finally replaced the TouchScreen, I installed the 2016 model unit with a 2016 AHU (aka CD player). These were driving the Harmon Kardon Logic 7 amp. As it turns out, the Meridian amp is from what I can tell, backward compatible to the HK system, BUT the HK Logic 7 amp IS NOT forward compatible with the Meridian TS and AHU. Hence why only the front door speakers were working.
So, now I have my Logic 7 amp back in my 2012 and the Meridian amp is "back" in my 2010 and everything is finally working as it's supposed to.
Hopefully my pain and stupid mistakes help to steer others down the right path.