Spectron's sound, in my system, in my view and based on my experience is simply an open window into the music. First thing that people comment on when they hear my system, people who know nothing about stereo systems but know a thing about good music and love good music is " Wow, that sounds really clear! " Music sounds so natural, so layered, so effortless, that it's a very addictive experience. I have excellent components in my system, but I truly think the Spectrons are the best I have, since they made the most improvement in the overall sound.
I've been a little vague in my description and intentionally so. When you hear the Spectron you hear music. If you're an audiophile and dissect the sound into bass, mids, treble, soundstage, PRAT, i challenge nonbelievers to find me any single amp doing same or better than Spectron in any 2 or more categories.
As far as name recognition, a valid concern in my book as well, Spectron is an established name with an excellent reputation, while Krell and Levinson are simply names with a good reputation back in the '80s and '90s but who simply can't keep up with today's best. Just listen for yourself. I think it's an insult to Spectron to put Spectron, Levinson and Krell in the same line. Buck for buck, it's simply laughable.
I own Spectron M3 SE w Bybees and V-cap. Also Von Schweikert VR7, Audiologic 34MXL DAC, Benchmark USB DAC.