Just thought I'd chime in here for my first impressions, coming from a '14 with the Alpine system.
While I'm not an audiophile, I am an audio enthusiast with decent experience in home theater. I'm familiar with and have set up room correction calibrations, acoustic treatments to manage room modes, manage secondary reflection points, etc. I know what good sound is. There's much more for me to learn, but as I grow older, my hearing doesn't keep up with what I'd "like" to hear.
I've never expected audiophile quality from a vehicle sound system. Even the Bowers & Wilkins system in the Volvo's (one of my favorites) suffer from some issues, mainly the environment; it's not a proper audio environment.
The '14 with the Alpine system was fairly good. Without going into a full review, I found it decent all around, regardless of input (SD card, USB, BT, etc.). Satellite radio… forget it.
I've only had my truck for a week, and minimal seat time. So take the following with a grain of salt:
My '21 with the HK was a disappointment to begin with.
I've learned the source matters greatly on this unit, more so than I've experienced with other systems. Bluetooth streaming of Spotify (My streaming app of choice) was relatively flat with a narrowed sound stage. Worse than my '14 for sure.
With the same settings, Android Auto resulted in a dramatic improvement! Finally, I could hear what this system is capable of doing. Wider sound stage, good SW performance, vocals are very clean.
I find the transition of mid to low frequencies between the speakers and SW to be too dramatic. When you hear sound coming from the SW, you know it's coming from the SW. It should be "invisible" to the ear. The low pass filter should have a range, not a sharp cut-off. Additionally, some of the high frequency sounds can be a bit too bright/harsh.
I will spend some time with my SPL meter and frequency sweeps to find the best settings for the EQ (though there's not much adjustment to play with).
This might clean up the mid to low freq transition and subdue the high frequency a bit.
XM has never sounded good to me; Ever. This system is no exception. I've had folks argue this point, I then listen to their system and find it to sound compressed (think low bit-rate MP3). Some channels are better than others, obviously a bandwidth priority.
I'm definitely satisfied with the system.