a short update. Thanks for all the recommendations. reading yours and checking other reviews I decided to get my shortlist in a head to head shoot out [emoji4] Vincent 237MK (German hybrdid monster 2x150W), Naim Atom (solid state, one of recommended amps here, 2x40W), Unison Research Simply Italy (full valve 2x12W) and my nearly 30 years old Sony f519R (solid state, I guess 2x130W). And to make it short, my order from the good to the best matching would be: 4 Sony, 3 Vincent, 2 Atom and 1 Unison. I wrote from good to the best, because they actually all sound good including my old Sony and I cannot say anything but good things about those amplifiers. I think this is also because heresy IV are such a good speakers.I guess anything you hook up to will sound reasonable probably:) I had them only for 3 days, so this is not a proper testing but still the choice was not that hard to make.
OK few words on the sound and some explanation. I would say that all the three solid state amplifiers sound pretty similar. The Vincent's power amp makes it sound as a solid state, and actually it was a bit brighter and sounds were less glued than in case of all the others. I had a hard time to pick my preferred sound, until... I started the Unison amp. Not in every song, but in some really a magic is happening comparing to the all the rest. I guess the sound is not neutral, it is sweet comparing to a bit dry sounding SSes, high frequencies are rolled off - it is not a reference sound, but still (at least for me) it sounded great. Guitars, voices, drums sounded very realistic and natural. And in some cases I got a feeling that the stereo separation is better. In some recordings there was an impression of a surround sound when the rest of amps was a bit more 2D. Unison has this third dimension. Although the stage seems to be lower than in SSes (I guess because of highs roll off). There is a bit less detail /resolution, highs are not that crisp but overall felling is that the music sounds right, as it should be.
So being fully aware that the amp is not neutral and lowers the stage ... I picked it [emoji4] it just sounds good with Heresys. This is just my taste, maybe someone else would have another opinion (although my wife and my brother sheared my view).
I want to add on more thing. Returning Naim Atom I was offered to check home a Chinese high end amp Line Magnetic LM 34ia. This is a tube, 2x40W, point to point amplifier. I must say it looks impressive and sounds very good, but... again I preferred the smoky sound of Unison more. Maybe for electronic music it had a bit more live, but in reproducing voices and real instruments Unison is a master in comparison.