Although design can remain the same, better capacitors, faster diodes, higher quality resistors will make a difference.
There is one variable we can not quantify, and that is "hearing"; some of us can hear better than others. Although I have never heard a class D amp, I can not imagine one as good as a tube amp; however, as good as a SS amp is conceivable.
If people listened blindly, I bet they would be willing to settle for a cheaper SS amp than the one they were lusting for, but there are those with exceptional hearing.
All the nuances in music only come through in the best systems, which is why the resurgence of analog; there's nothing like the best vinyl.
In the conversations we have, there isn't much difference between, we'll say SS amps in the high end. Those who can hear the differences, are most fortunate.
