100thMonkey suggested I go 'public' with my review. Thanks for the encouragement! Here it is.
This review is based on my Get Amped test drive in VIN#115 in Portland.
Audio Quality:
To be honest, the sound system was crystal clear, but I expected it to be louder. It's pretty loud, probably louder than I would want it to be while doing a long drive - and I tend to crank it. At full volume, there's no distortion or crackling, so I suppose that's good. Some have said that the bass is deep enough, some have said that it isn't... I haven't tested the settings, eq, etc. enough to be sure, because I didn't want to make my kids' eardrums bleed during the test drive and didn't want to be "that guy" in the showroom.
Volume granularity:
Also, some on these forums have said that they want more granularity on the volume controls... I don't think the same way. I want a nice low volume for background music while chatting, and a nice high volume for cruising along. Maybe a couple of steps on either side of those two focal points on the scale to adjust for pavement quality. What else do you really need?
Speed Adaptive volume:
I was wondering about adaptive volume for speed. After doing the test drive, I think I know why this wasn't included in Model S. That feature exists in ICE cars to overcome the engine noise of the car. In Model S, at 80 mph, there is no engine noise, and the road noise isn't loud enough to drown out the music previously set at a comfortable level. So, that's another feature that can be made obsolete by EV advances.
Formats:
I am still planning to do finish checking on the support for FLAC, OGG, and other lossless formats, and multi-channel audio support (request is in to Troy). The car is not soundproof, and it is doubtful anyone could make out the difference between lossless format and high-bitrate MP3 format while in motion on the road in this vehicle. [ please no trolls - show me the proof! ] The still-audible road noise in the Model S would would drown out the ability to discern that much from the music.
Overall, I believe the premium sound system is better than the non-premium, and that a better after-market system that so tightly integrates with the rest of the car would be more than $950. So, I'm getting the premium system as a delivered option.