@tomthiel Thanks for the detailed response to my questions. You may consider yourself an electronics layman, but you still know a lot more about this stuff than I do.
Given that the 2.2 appears to be easier to drive than the 3.7, it sounds like the AHB-2 should have enough power to handle my 2.2s if I decide to try one. (By the way, my room is about 3800 cubic feet, though with some large openings on two sides.)
I'm still trying to learn more about the distortion profiles of amps and their audible effects. The Benchmark website has a lot of interesting info on its products, and I even understand some of it. Jon Siau at Benchmark talks about providing electronic compensation to reduce second and third harmonic distortions (through their DAC, I think) as part of the attempt to reduce all types of distortion as much as possible. In contrast, Nelson Pass says that his listening tests at Pass Labs have shown a general preference by many listeners for the sound of amps that don't work too hard to suppress lower order distortions. Ralph Karsten at Atma-Sphere says that second and third harmonic distortion is not annoying to most listeners and actually helps mask the higher order distortions that give so many solid-state amps a harsh or overly bright sound. Siau, Pass, and Karsten are all highly regarded designers who use both measurements and listening tests to design their amps.
On the surface, it would seem best to reduce all distortions as much as possible, and this appears to be part of Siau's approach. On the other hand, there seems to be general agreement that the harmonics in recorded music reproduction are not identical to the natural harmonics in real-life musical instruments. This raises the question whether sound would seem most natural and real if all distortions are as low as possible or if the harmonics profile of the gear used to play back recorded music needs to come closer to matching the harmonics profile of real instruments. This sounds like a situation that will demand some actual listening!
Thanks again for your help in thinking some of this through.