So i've been researching using everything I can find on this sound system. Not surprisingly, complaints are plenty, so I knew that if I searched enough, I would find other audiophiles who chose to do something about this system. I found a hint in one driver's evaluation where he said it sounded like the center channel level was just too high. Then I evaluated same on my own system and realized that it did indeed seem as though the center channel was overpowering everything. This was reinforced by the fact that as I faded the sound to the rear, it started to sound better.
So I decided to take a look at what lays under that trapezoidal grille. Turns out theres actually an array of speakers under there. two 2.5" drivers and what appears to be a tactile transducer of sorts...all this covered by a heavy gauge steel plate? Tough to wrap my mind around this design - take two low-quality, tiny speakers, cover them with a steel plate, and expect good sound? Perhaps there is some magic here but it's tough for me to see. I decided to test my hunch and simply disconnect the whole mess. So after taking apart the entire center section of the dash, I was able to access the wire harness and disconnect the speaker. Guess what? MAJOR improvement. I rebalanced the system (ended up with fader at -2) and re-tuned using the crappy EQ, and I now have passable sound! It's still very meh for what is billed as a super-high-end system, but it's at least meeting modern standards. I can live with this.
The next issue that I plan to tackle is the super-harsh metal-dome tweeters. I'm not positive the issue lies completely with the tweeters themselves, but swapping them for fabric dome units with better range can only help. Then I will find out if there is in fact an underlying crossover issue.