@holmz
Good question.
Sound quality is both objective and subjective evaluation.
For me, it began very subjective… chasing heavy bass, quieter noise levels and greater detail: making rock music more impactful and dynamic.
But over time, I realized that to make all music sound better on my system I needed to improve it objectively. For twenty years I worked diligently to “learn” what real music sounds like at every opportunity… I listened to individual instruments, and went to hundreds of acoustic concerts. I steeped myself in live music to learn its nuances. This is not as easy as it sounds. First you have to realize that amplified concerts are not helpful… they are too influenced by the amplification and venue. You have to listen to it a lot and learn terms to characterize it, to adjust for the venues. But like anything else many hundreds or thousands of hours allows you to develop an in depth understanding… and this gives you an internal empirical ruler.
This approach slowly began to effect my appreciation of reproduced music at first. Then it radically began influencing my choices as I learned what real music sounded like. All, genera of music sounded better and better as reproduced from my system.
So, while even for me sound quality is still a combination of both, it is much more objectively driven.