Searching for the most "accurate" speaker (below 15K)

@vermeer 

First of all, congrats on the Nagra Classic Amp. I've heard it once and was amazed by its pure performance and amazing bandwidth. Even at very loud levels with the orange clipping light activating, it never lost its composure, not one bit.

I've never heard the Paradigm Persona 3F or the Kef Reference 3 (would like to) but I have heard the Focal Sopra 2, many times in fact. I've never heard that speaker sound good but for one time. And that was with PrimaLuna and Audio Research tubes. I still find that speaker to be quite clinical and not to my liking.

Back to your Nagra. I heard it about a month ago in stereo mode with the matching Classic Pre. Source was dCS Debussy DAC with Network bridge and AudioQuest cabling. Speakers were the fabulous Wilson Audio Sabrina's. It was really really good. It may be my favorite pairing of the Sabrina's that I've heard. I can tell you first hand that this is a very well matched system and so I know the Sabrina's work very well with Nagra. Dave Wilson indicates that he uses Nagra in a video I saw on the tube. Search Youtube for Wilson and The Audio Salon in Santa Monica for a video of Dave talking on Nagra. The owner of The Audio Salon, Maier Shadi, is a true gentlemen and could help you in your search. I only know Maier in that he demo'd that system for myself and a friend. I have no other connection with him but can highly recommend him.

Absolutely agree with audiotroy on the Personas.  And no I don’t know him, in fact I have even complained about his posts in the past, (although I don’t really have an issue with them 99% of the time).

It just so happens that if you have heard the 3F’s PROPERLY set up, they are unreal.  

I think here the room really is the elephant in the room. 20 sq m is small, and too small for great dynamics or deep bass. That is just physics. Depending on the precise dimensions, the Schroeder frequency will be somewhere in the range 175-200 Hz. Below that, there is trouble. Put some full range speakers in a room like that, and you will regret it: you will suffer bad room modes at quite high frequencies compared to bigger rooms, and their upper harmonics as well.
So I was thinking that perhaps you should start bottom up: how can I get quite extended but very clean bass? Only when you have sorted that can you move to mid range etc. As others have said, bass traps may help, but in a small room there is little space for them (and perhaps even less tolerance). So you have two options. The first is to avoid much deep bass altogether, using mini monitors like the Harbeth P3ESR. Perhaps you could move up one size with something like the Harbeth M 30.1 that I suggested earlier, but that is about it. But there is an alternative, and it is to use multiple small subwoofers, at least two but for the best result four. See here for some introduction to the relevant research: http://www.acousticfrontiers.com/20101029using-multiple-subwoofers-to-improve-bass-the-welti-devanti...
By themselves mutiple subs already give a much smoother result, but if you then add dsp room eq the benefits will be available over a much larger listening area.
After that, and I think only after that, is it time to think about the main speakers. Avoid getting big ones for that. If money is not tight, the forthcoming DSpeaker X4 pre amplifier/DAC/room eq may be interesting as it gives you the opportunity to also equalize the bottom end of the main speakers. But realize that the higher the frequency that you equalize, the smaller the equalized listening position.

Open, natural, truthful, dynamic, Boenicke W11 or W13.