My guess is that it is probably not that much different...
I have found much value in the RTA graphs you have shared (both here and at the other forum). They have confirmed what my ears were already telling me.
I really do not want to go the MS-8/LC8i/3sixty.3 route. Honestly I will probably just replace the HU and bypass all the factory wiring completely instead. I am not looking for perfect right now, just better.
I already upgraded the dash speakers and the sub so I am getting plenty of highs and lows.
The piece that is missing is any real presence of mids. The doors perform at such a low volume that they have virtually no impact on at all. I turned of the crossover on the sub amp figuring that the factory sub signal was already trying to compensate for the weak door speakers but the sound gets real muddy a upper volumes.
So here is what I was thinking as an intermediate solution...
My first thought was to tap the signal going to the doors only and feed it to an amp and upgrade the door speakers. I realize this will do nothing for the weird curve, just hoping that overall it would level with the rest of the signals from the other speakers.
I was almost ready to go this route when I saw the post about the upgrade Kicker amp. So then I figured if there is a solution that does not require any rewiring then it is worth a look.