"...PUNCH was about the same, although the brighter sound of the KT90s made the high-frequency leading edge of transients seem a little "crisper". The 90s seemed cleaner sounding and more detailed at first, but got duller and more wearing...etc"
I do not know how can you, or anyone else, tell such a subtle difference? I wish i have such a delicate hearing as you.
What is "punch?"