I have not heard the Merril or Atma-Sphere GaN amps.
I can only speak directly about all the tube and solid state amp I have owned.
And to a lessor degree, amps that I have heard at shows and friend’s homes.
The review by @jjss49, I feel, gives an accurate breakdown of AGD’s performance.
IME, the AGD Audions produce SQ that is different and unique. Partially, AGD’s designer clearly has a great ear. And partly, he has created an amp that reproduces all the “broad strokes” and, especially, the subtitles that take SQ from great to “real”. One key of these is hearing the phrasing of musicians. Something that is both subtitle and profound. I have only heard this quality with AGD.