Open up a 20YO SS amp and one built today and you're not going to see much in the way of differences ihn any of the major parts. In fact, most of the parts will be made by the same companies!
20 year old solid state technology.....
I have an older Belles 250 amp...class a/b...and have been amazed at how this amp sounds even in regard to the best that is out there today...regardless of its age...which is circa 1987...at any rate...was this statement product by Belles that much better than the competition during its time...or has electronics at this level not evolved that much outside of "subtle refinements"?....