Classy,
You do not mention the ceiling height but as it is an office I will guess
between 8-9 feet.
You are fortunate to have a great shaped room that will help any speaker.
If you have flexibility in laying out the desk in the room the sound will be better by employing the long walls for speaker placement. Yes you will be closer which
actually improves the sound. Instead of placing the desk between you and the
speakers why not place it on one side or the other from the listening chair?
The suggestion for using DSP is a good one.
If you are able to utilize the space to it best advantage any speaker you choose
should be pretty good.
As to which brands-you inclusion of the ATC makes me wonder if warmth is
really your preference. It is a very good speaker and perhaps for classical
very good. But I have also heard it is not good for lower listening levels.
My brand suggestions would be- Fritz Carrera 7 BE . Great for low level and detail
yet very warm. At $3k a total steal. As good if not better than the Pulsars for my
ears. Yes I did an a/b in my home with these two.
The Dutch and Dutch-also had an a/b in my home- are better in lows and maybe miss than the Fritz but you lose the highs which are amazing. Fritz 7BEs need a sub or two.
Borresens are a great sound and important to audition.
After that I would consider the Franco Serblin Essence MSRP $20k but
some places will discount. This one may be the best for the classical you listen
to. They are to me the prettiest Box speaker going.
Good luck my friend!
Remember only your ears count in this decision.