Tube amplifier suggestion for 101 dB speakers

You might also consider this:

http://www.decware.com/newsite/SE34I.htm

My experience is that you sure don’t need - and probably really don’t want - 75 watts for each of those really efficient speakers; because amps just sound better when they are using more than just a tiny fraction of their power.  I mean, I’m not an electrical engineer or anything like that - somebody more knowledgeable than I could explain it - but I believe this is why a lot of receivers and amps had loudness switches or dials.  Turn the main volume up and flip or adjust the loudness when playing at low volume.  

This point may of course be secondary to your decision.  But you really don’t need 75 watts per channel for really good sound.  I think using the amp in the link above or another of the few competing American made little SET amps is the way to get really nice sound out of super efficient speakers like yours.  

So, maybe you’re wondering if they will play loud enough without distorting.  Don’t be mistaken... you can still get your speakers loud enough to have the neighbors call the cops... with the volume knob less than half way up.  

That's right, I'm not driven here by need of high power.
The speakers are highly efficient here with 101 dB, but also they are 4 Ω in impedance which I guess will limit the amp selection.
Here is the Atma-Sphere S-30 but they want 8 Ω and up speakers at least. This is an OTL type amp.
Then come the SET amps, I think this is the category what I need.

You're on a good track. Even with SET amps, there are a number of different tube types which each have their own relative strengths. For example's sake (please don't flame my oversimplification here):
845 - a bit more powerful, good dynamics & bass slam for a SET type
300Bs - beloved midrange, magical vocals, acoustic guitars, cello, etc.
2A3 - great imaging, traditional warm tubey colorations
45 - lowest output, need highest efficiency speakers

Try researching articles like this to learn more on the differences:
https://hometheaterreview.com/whats-so-irresistible-about-a-single-ended-triode-set-amp/  Sorta simple, but it's a start. Cheers,
Spencer

piramis OP
 The speakers are highly efficient here with 101 dB, but also they are 4 Ω in impedance

Yes as I said before, and that’s a nominal 4ohm, it will have dips even lower than that.
Look for an amp that has a 2ohm speaker tap just in case beside 8 and 4ohm.

The 100w per channel Music Reference RM200 has a 2ohms tap which should still give enough watts from that 2ohm tap for your 101db speakers in case you need to use it.

http://www.ramlabs-musicreference.com/music_reference_rm-200_hybrid_power_tube_amplifer.html

Cheers George

I kind of understand now these particular types of tube amps and how should they be matched.
And more and more I think that the problematic thing here is the 4 Ω / 101 dB combination for the speakers I have.
So there is no need for high power, that's a SET amp then, class A and no need for biasing anything. Cool, but I need a stereo, preferably with XLR in. I can hardly find something used under 3K.
I thought a BAT VK-55 would be good, but that,s not a SET.
I'm telling this territory is not easy, a push-pull would be much easier to pick.