@lonemountain. Thank you for your feed back.
b_limo2's suggestion is a good one. I think overall more people who love orchestra, jazz, piano would like the transparency of the newer generation SCM 19's (the one in the curved box) because of the higher end drivers. For those into rock music, pop music, radio or cinema the SCM 11 is the deal. All ATC drivers are still hand made.
My theory on ATCs sounding better louder is simply that they're accurate so they sound more like live music the closer they get to the volume of live music. Other speakers are less dynamically accurate but sound subjectively better at low volume.
I wonder if there is a relationship between the ability to handle high volume and better sound at high volume. What speakers sound great at low volume but can handle high volume?