Specs aside, you need to sit in both to figure it out. Audio systems tend to be ranked subjectively rather then objectively.

 

For me, ML system is better. No doubt.

 

Was not a deciding factor in our purchase but I drove a few non ML premiums before buying our ML luxury. I definitely noticed a difference in sound clarity.

 

last week i compared ML to non ML back to back the same day. I have the ML, got anon ML loaner had it for about 7 hours drove 4 of those 7.
ML lacks bass, sounds a bit muffled. I adjusted the eq but it just wasnt as good as the ML.
the ML on my '12 sounds much better than the '19 non ML
in fact, my '12 ML is good enough that I haven't changed out any sound system components, very rare for me.

 

In a non-ML, Premium trim, 2019 GX, what sound system upgrades could you make for less than $1K, which would substantially improve sound quality?

 

You can replace the speakers.

https://www.clublexus.com/forums/gx-...r-upgrade.html

 

Replacing the head unit isn't an option as it is so tightly integrated with the rest of the electronics, so, like tecman said, the only real options are the speakers and amplifiers.

But we all need to realize that a car - and certainly not one like this - is ideally suited for quality audio, so a really good system isn't going to make that much of a difference.