Audio Research vt-100mk11 vs vt-100 mk111

What are the sonic differances between them? Which is better? Why did arc drop the vt-100mk111? I own Aerial model 9's which amplifier would be better vt-100mk111 or mac 402?
I traded up from mkII to mkIII and found a very noticeable and positive difference. There was much greater detail, separation of voices/timbres, etc. A lot more information and a lot more music as a result.