Best power amp below US $ 20.000,00 ??

Elberoth2, in your 14' x 19' foot room you may not need a 'big amp' that is typically associated with Eidolons.

you mention your interest in an 'SET mid-range' yet have a 87db, 4 ohm speaker. depending on listening habits, finding an amp that can control your speaker and also give you the midrange magic you seek may be a challenge.

i have not specifically heard the Vision version of the Eidolons.

you might consider the Swiss made darTZeel. it fits your price criteria and will give you a magical mid-range clarity (but not added warmth or shimmer). normally i would not recommend the darTZeel for the Eidolons; but with your particular sonic priorites it may come closest to the ideal.

some SET fans (both 300B and ML2.1 owners) that very recently visited my room commented on the very tube like naturalness they heard from the darTZeel. they could not believe there was no tubes in my signal path from what they were hearing. yet the darTZeel is quite dynamic and extended top and bottom.

if you were to eventually upgrade to the darTZeel battery powered preamp you would have perfect synergy.

The amp I liked best so far was a SET amp based on a single GM70 triode - 30 watts of pure triode magic. I still want something of the shelf.

This is the off-the-shelf version of what you are describing.

Next week I’m gonna try some local ICE based amp and a Nuforce 9s. The next amps that are waiting “in line” are Krell 400 & 700cx, some Classe monos, Plinius SA102, Pathos In-Power, Pass X-600.5, Electrocompaniet AW-400, Mac MC-501. It is gonna take some time though, since I ALWAYS borrow the amps for at least a week for home audition.

In my opinion, you are wasting your time with all of these amps. Not one of them resides on the same sonic planet as what you state as your preferrence: "that amp had everything I was looking for - fine textures, microdynamics, holographic soundstaging, harmonic lushness, natural timbres." Those listed here will not meet your criteria. DeHavilland will. Wavac, Lamm, Joule, etc., but not these.

Best of luck.

The Tom Evans Linear A is another option. Gliderguider loves his. I've not heard it, though this review calls it a home run. I have heard the DeHavilland, several times in fact. It has exactly the qualities you describe in the DIY amp that you heard.

Boa2 -> I'm aware of deHavilland amp. The only thing that is putting me off that amp is the fact, that the DIY amp I mentioned was MUCH more sofisticated than deHavilland offering: hand wound transformers, all NOS paper-in-oil caps, all tube rectification plus the GM70 was driven by 300B triode. deHavilland looks like toy next to it, although a much better made one !

Sbank -> I haven't tried any OTL amp so far (the only one I could possibly borrow is little Graff GM-20 OTL - way too underpowered for Eidolons, I guess) but I heard many times that all OTL designs are best suited for 8 Ohm impedance speakers, or even higher. The Eidolons Vision drop to 3,6 Ohm.

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Today I brought home the Plinius SA 102 amp. I know that it is much cheaper than other offerings we are discussing here, but my dealer didn't have the more expensive Plinius models on hand, so I decided to listen to SA 102 first, just to see If I like the Plinius "house sound". If I do, I may investigate the more expensive models. If not - well, I will move on.

deHavilland looks like toy next to it, although a much better made one !

Considering that you could probably get the $10K deHavilland for several thousand less than retail, the additional $13K to your budget limit should get you what you want without much difficulty. Of course, if you require week-long auditions of each amp, then these long-distance suggestions are a moot point.
Good luck in your search.