15k USD Speakers for Classical and Pop Extended Listening, Near setup, Low volume

Sonus faber Maxima Amator. Right in your price range and ticks all your sound quality/characteristic boxes. 

Recognize I speak from personal preference and you should purchase based on your preferences and based on audition. I find KEF a little aggressive on top. I find the ATC could be a little more rich in timbre but overall a great performer.  I never heard the Monitor.  As I have in past posts I recommend you audition Vivid. The models I recommend are the Kaya 90 and better the Giya G3. I chose the latter.  They well perform like the ATC but have a rich timbre.  You will need to get past their unique aesthetic.  I love the look.  You will have to go preowned to be at your price point. They come up occasionally on this and the other site.  My room leaves much to be desired due to the WAF.  They still sound coherent, balanced, with a wide and deep stage.  I sit about 7 feet from the speakers and they are extremely coherent and balanced with bass better than ATC and one of the best high ends.  I recommend after market vibration products of your choice to extract full potential.  Read pro reviews and more important, audition.  Listen to how natural cymbals (the hardest instrument to get timbre correct) are reproduced.  Let your own ears/mind make the choice.  Good luck

No recommendations about speakers from me on this one, but just a remark about the poster advocating for placing the speakers BEHIND the listener. I could not disagree more. As far as I know the human ear is designed with the full opening in FRONT of the ear and a flap in the back to better direct the sound into the ear. Just saying, why fight mother nature on this one.

ATC SCM40 may be a great choice...If you like a flat and still musical sound ATC is a great choice.

Since your username is ilikeclassical ..you could try a pair of Audio Note UK Type Ks...they come in many performance levels and cabinet finishes...Great at low and medium volumes ...A small speaker that can reproduce solo piano in a fantastic, realistic manner in small rooms.

looking at the photo, I am confused. To say it is not conducive to good imaging, clarity, etc. would be putting it lightly. Imaging the soundstage as a plume or a pear. Your screens, your desks slice up that plume and you won't get much out of your 1000s of dollars, for the result you should expect. You could be better off with nearfield listening, having smaller speakers by your desk. You would save a lot of money. E.g., Dynaudio Evoke 10s or Harbeth P3esr and you can also add a sub away from you, by the wall.