Blindjim ;
I took a peak down this rabbit hole as well as the one next door addressed as high efficiency speakers .
One of the responses by Ralph addressed the difference between the requirements of SET amps and PP amps . He stated the same desirability of running a SET at a maximum of 20% power . But then he stated how PP amps really needed some power to sound their best ... like maybe 20% + power .
After peaking down the HE speaker rabbit hole , I found it difficult to find speakers that were affordable , at least halfway aesthetically pleasing and suitable for my situation .
Right now I am content with what my current PP amp is doing and seeking improvements in other directions . I have spent quite a bit of time rolling input , driver and power tubes to get where I am .
While I still may seek out a SET amp in the future , I think that I would have an easier time finding one in the PSET realm where speaker choices would be more plentiful due to the added power of the topology .
Have you given any thought to PSET's ?
On a different note...I believe that you are in the TB area . Where would you go to hear different tube amp demonstrations ?
Good Luck .