It seems that the SET amp magic doesn't happen with all speakers. In other words...you can't just plunk any SET amp in front of any high efficiency speaker and be certain you will get the "low level transparency" you referred to.
Some SET amps are not capable of SET magic.

And you are quite correct, SET amps are especially finicky when it comes to speakers.
As everyone knows, or at least as everyone should know, building a system around the best possible speakers you can afford that are appropriate for your room makes more sense than building a system around a finicky amplifier with modest power output that’s going to determine what few options you have for loudspeakers.
Oh,and when it comes to low level transparency, The best Class D amps have it in spades. After all the tube amps I have owned over the years - it’s been two years and I’m not missing any of them,

or the type of speakers that came with the territory of owning a SET.
