Jerome, I understand. It is difficult to get Shindo to sing properly. Just because a speaker makes sound, doesn't mean the gear driving it is giving it its best. There used to be a time when speakers were ultra-efficient and impedance friendly for what was the amplification of choice, the only choice... tubes.
That was before transistors were invented. These days speaker manufacturers pay much less attention to the efficiency and impedance that often swings wildly. Who cares about the speaker specs when any deficiency can be overcome with power! Power is cheap, especially now with digital switching amps, class D. Except that it takes many bandaids to cure the multitude of sonic deficiencies to make a SS amp sound great or at least tolerable. Sterile, grainy, lean, thin, etc..... sure, throw enough negative feedback into an amp to make it behave and it will measure better but.... what about the sound???
Fortunately we live in times where many manufacturers are able to make us more or less happy with their designs. It was much easier to make a tube amp back in the day that sounded good because of the inherent advantages of tubes, soft clipping, even order harmonics (depending on topology of course) but they were limited in resolution and "air" as well as "bandwidth" because some of the vintage parts were not up to par to today's standards (some vintage parts are actually quite good sounding). Today we have even better tube amps but we hardly have speakers that mate well anymore with the inherent limitations of tube designs!
When we consider SET amps, I'll quickly quote wikipedia, "SET amplifiers typically show poor measurements for distortion with a resistive load, have low output power, are inefficient, have poor damping factors and high measured harmonic distortion. But they perform somewhat better in dynamic and impulse response. Also, SET-amplifiers allegedly (there is little agreement on this) sound good at low power levels without the perceived need for higher sound levels like transistor amplifiers allegedly do".
We quickly realise that we need proper partnering speakers.
Not many out there, are there?
Of course the Shindo amps will sound different as well, the fundamentals of Push-Pull vs Single Ended Triode are a bit different too. Different tubes have different flavor as well.
I don't think it takes a genius to figure out that going the low powered route, it takes some effort to put together a system that will do all the components justice. It is a more challenging path and well worth it to some and not so much to others. To each his own.
I think you already came to that conclusion when you experimented with VERDIER triode amps. They made sound come out of your PMC speakers but you didn't fall in love... It will not be any different with Shindo! While Shindo may be magical, it doesn't have the kind of magic to overcome simple laws of physics and electrical theory.
The McIntosh MC2301s are designed to work well with just about any speaker and have the guts to do it too.