Cube Audio Nenuphar Single Driver Speaker (10 inch) TQWT Enclosure

At 92 db/w efficiency, whether or not something like a single-ended 300b or other small triode will work depends a lot on how loud you like to play the system.  With most single driver systems, you have the BIG advantage of the speakers sounding really good--lively and engaging--at quite low volume.  I liked the Nenuphar playing at low volume.  I liked it less when the volume was cranked up.  That is not a big deal to me, because I like low-volume listening, but, it is something to consider when looking at this kind of speaker and the right amp to work with the speaker.

I am not surprised that people report good results with SET 2a3 and 300b amps.  I generally do find that most people overestimate the amount of power they really need.  For the vast majority of time, one listens at levels where a watt or two is enough.

But, there will be some limitations with these types of amps and speakers in this efficiency range.   With really demanding music, such as large-scale choral music, at crescendi, one will hear the effects of compression--the music stops getting louder and it becomes more muddled sounding.  I hear this to some extent when using my 5.5 watt amps on 99 db/w efficient speakers.  It is not a big deal to me; I don't attempt to listen to Mahler's 8th at "realistic" volume, but it may be a bigger deal to someone else.  This is something everyone has to judge for themselves.

Hard to imagine there is more to come from these wonderful speakers as I  reach the 100 hour mark.

Stephen, I found there was "more to come..."   :  )

Let us know what you find.