Quick update: I was able to audition Constellation, Boulder and D'Agostino amps yesterday. The Constellation Stereo, the Boulder 1060 and the D'Ag monos.
I found the Constellation very smooth, yet detailed, but lacking a little in bass punch - but it could have been the room.
Next up was the D'Agostino. By far, the most musical, liquid sounding amp I have ever heard. They don't sound like other amps. They are like someone took the best of solid state and the best of tubes and smushed them together. Only downside is those little buggars get hot!
Next up was the Boulder 1060. I don't want to start a whole big thing, but lets just say, it was an amp for me. It sounded a little dated and it was like listening to an amp design that is well, 10 or 15 years old. Certainly not SOTA IMO. YMMV.
So for me, the three best SS amps I've heard are Soulution, D'Agostino and Vitus. Vitus is the big sleeper in this group. I would say, picking one, would depend entirely on speakers, the rest of your system (preamp, cabling, etc.) and music preference.
Mike