In search for speakers of "natural" sound

You should look at Revel and read this book by Dr. Floyd Toole:
"Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms".
The concept is you want speakers that measure flat on and off axis. 

All of your other equipment measures flat, why would you want speakers that don't?

Silverline SR17 Supreme (USD $7500). I'll have a review coming out imminently, but I believe this is one of the premiere speakers < $10k for reproducing acoustic music. Not the best at electronic/harder music, but great for e.g. classical and jazz - very organic and balanced with just a hint of warmth. Very high resolution too, without being too fussy - a forgiving load and easy to match with both solid state and tubes.

Cheers,
TAWW
http://taww.co

Spatial Audio speakers have no cabinet coloration , being open baffle. They have no dynamics compression being pro audio drivers . I have had comments on how natural my Turbo 3's sound . Give them a listen or order direct for a trial period .

I'll add another possibility here, which is that the audio magic you seek may lie more in the recordings that you choose to play than the equipment on which it is played. There are many brilliantly recorded albums that playback on even somewhat modest systems with a spooky, they're in my room, realness. It could just be that your sources aren't that great to begin with and nothing is going to make them sound the way you'd like. I know I have many albums that are disappointing from this standpoint. I still listen to them because I love the music, but it doesn't give the wow factor.

I don’t see any mentions of speaker placement ... you can get a lot more natural sound if those Harbeths are not jammed against a wall with a bunch of gear in between them.