John Iverson, designed the Eagle 2 and later the 7A. His work was ahead of its time, as was he. He commented to me that designers did not understand the difference between voltage and current, and how manipulating them differently was the secret; I frankly didn't understand, and may have misplaced the words somewhat, and these are distant memories at best. However, his amps, and their sound are not distant memories to me. They were excellent! I put several Eagle 2's at $595.00 with the Conrad Johnson, Premier 3, a financially imbalanced system, but sonically spectacular.
I remember them sounding, generally, much more like a Bryston, though much more refined by comparison, than any of the others you mention. The Krell, for example, is much too hashy in the higher frequencies to have similarites in anything but the bass.
For its day the 7A was as remarkable as John, ahead of its time, just like him. With the difference in technologies, over the past 20 years, even at its level, I would doubt, but not emperically, that it could compare. Transistors are faster now, and more linear; circuits, and knowledge of proper placement of items on the boards, have evolved so much, unlike tubes. It is odd that a 1930's design may actually sound wonderful, even by today's standard; there have simply been too many advancements in the internals of solid state.
Plus, as someone mentioned, repair potential is not great.
Where is John? I would like to hear if anyone knows. He supposedly disappeared quite mysteriously. Someone told me that he was working on, 'Eyes only', Government weaponry systems, and one day, just vanished. This is all true. Stange, I admit, but true.
If any audiophiles familiar with John have any information I would like to know. He was a remarkable and brilliant man. If he were around today, working in audio, he would shame the lot of them out there.