The treble is already bright enough at mid-setting and I don't turn it up louder than 12, so I haven't had any problems. Actually, the Lincoln Revel system compares well with the MB Burmeister and Volvo B&W systems from my test comparisons.
Your complaints with the exhaust drone also makes me think you have an issue with the active noise cancelation. The exhaust on the two Navigators I test drove were silent like the one I ended up purchasing (except for 10 seconds after startup). It was subjectively a tad quieter than the 2020 Expy Platinum I drove.
Either way, both the Expedition and Navigator are pretty nice overall. My point is if you are in the market for a Platinum Expedition, you should consider the Navigator as you might find better deals to narrow the price difference.
I'm not trying to argue about the exhaust, but I'm telling you we own BOTH and daily drive them and the Navigator is stupid loud in comparison. My wife absolutely hates the exhaust racket it makes. We've taken it in numerous times for the exhaust noise and they and we have put decibel meters on a brand new Navigator and ours side by side and they made identical DB's. The muffler just breathes too much and barks on the highway.
We had the amp on the active noise control replaced a month ago and it changed nothing. The dealer suggested that would help the noise and it did nothing.
My neighbor actually told me he hears my wife drive out on her way to work EVERY single morning. He asked me why we put aftermarket muffler on it, and I told him its all stock. He literally wouldn't believe me. He said he can't hear my expedition, but her Navigator just makes an annoying deep vibrating drone tone every morning she leaves for work.
My Lincoln dealer told me we were the 3rd noise complaint they received on recent Navigators and thats just how they are as they test them side by side with new ones. I tested them myself and they're just retarded loud. I'm looking into welding in additional mufflers into the exhaust. I'm just not sure if its the muffler case giving off the noise or if its all from the tailpipe. It almost sounds like its the muffler case resonating sound into the second row floor.