Wanted to update the forum folks. Thanks for all the advice.
Crutchfield has been great with advice, etc. Install instruction, etc. and became even greater when I talked to an advisor named Norm who in a past life was an installer. He has a tremendous amount of knowledge!
Installed Infinity Reference REF-6530cx with separate tweeters in the doors of my 2018 Accord 2.0 Touring. Followed the advice of Norm to also buy the Hushmat Wave Breaker Kit to apply to the outer door behind the speakers and also installed XTC 6-1/2" Speaker Baffles, 3-1/4" depth and using his instructions to cut out the backs of the baffles to allow the speaker to breathe. Tweeters needed some mounting modifications but Infinity supplies four different adapters of which one was rather helpful in the install.
Finished the car today. The front stage is fabulous now! I hear a substantial difference! Good, clear bass up front, no muddy sounds like before. Very solid mid range from the door area and those little tiny tweeters are just fantastic! In fact the front stage is so alive now, I don’t hear as much from the center dash channel which I believed was the culprit causing much of the hollow, dead, mid range sound. Being higher up, in the center dash, and bouncing off the windshield as well as the plastic back of the Infotainment display, it was adding more crap sounds than the rest of the front stage. Not so now… It just sort of fits in.
I can now move the fader more toward the back to actually hear something from the anemic back deck, so finally sounding quite decent with front/back separation and some bass from the rear.
I cancelled the order for the center channel dash speaker. Didn’t want to take half of the dash apart anyway. Don’t need it now. Which saved me $150 as they were only sold in a pair and quite a bit of tedious work.
The system still needs improvements, rear sub is weak and really all of the rear deck speakers are weak. But from my reading, the amp or DSP portion of the amp is apparently responsible for this via Honda design.
Even Sirius radio sounds good, which is saying something for their weak digital, low-Khz music transmission.
Haven’t tried my iPhone yet. That sounded the best before. Even FM was decent!
Next step may be to put all of my Apple ripped music on a USB drive and plug it in the center console and set it up for maximum KHz to equal whatever the Honda system will allow and play. Have to research this...
So, great day and I didn’t break anything in disassembly or in re-assembly!
PS: Don’t forget about consider adding the hush mats to the door body behind the speakers. Eliminates a lot of bouncing distortion from the metal body behind the speaker. Also add foam cups on both doors, per the Crutchfield guy. I can't say for sure they have made a difference, as I did not experiment with or without. For the $40, if that guy Norm liked them than I would follow his advice.
I am good for now. The whole system is revitalized. Maybe later will try something to help out the dead rear