I should also say that I am looking for very high performing GaN amplifiers to perform against some of the best / most high-end units out there, like the T+A A 3000 HV amplifier (which I own along with the T+A PS 3000 HV power supply), Audionet amps as @pennfootball71 mentions, or other Class D leaders like Aavik or Bel Canto Black. High bandwidth, control, transparency, and resolution are all important, but just as important is a completely organic, natural presentation with the proper use of harmonics and lifelike presence/immediacy and dynamics.
@greg_f I unfortunately haven't AB/ed Aavik against other amplifiers with the same speakers in the same room to be able to comment. I would say that Aavik 580 series is a cleaner sound, but still incredibly musical, than my reference T+A HV stack. The T+A has richer harmonics and a tad less control in the lows (Aavik is known for its insane damping factor and that is a large contributor to making Borresen speakers sing the way they do). My T+A is more natural, a bit less clinical, but at the expense of not being as lightning fast as the Aavik. Keep in mind that this was the same set of speakers, but in different rooms (I brought mine back to Next Level Hifi to compare) and different cables (Synergistic Research Galileo SX in my room vs their Ansuz DTC-2 loom). Gryphon has richer harmonics still over T+A, and I prefer T+A, which is why I became a dealer for them. Pass generally has less rich harmonics than Gryphon or T+A but has a warmer character to them. Vitus, I've only heard once, with Estelon Extreme at AXPONA this year, and though I've heard a few Estelon, I'm not familiar enough with what the amp was doing vs what the speakers were doing. In that room, it was a very burly, natural sound, but not as immediate and transparent as Aavik / Borresen combos I've heard time and time again.