ATC SCM11 thinking about a pair. Opinions.

I am going to ask for an opinion/thoughts (boy I asked for it now).

I am thinking of getting a pair of the ATC SCM11 for use in my office 12x14 Moon 240i a Moon 280D.

my main system is a 340i with the 260D and 280D SF Olympica Nova 3. 

Really depends on what kind of sound characteristics you’re looking for.  They will sound quite different from your SFs if that’s what you’re after. 
b_limo2's suggestion is a good one.  I think overall more people who love orchestra, jazz, piano would like the transparency of the newer generation SCM 19's (the one in the curved box) because of the higher end drivers.   For those into rock music, pop music, radio or cinema the SCM 11 is the deal.  All ATC drivers are still hand made.
My theory on ATCs sounding better louder is simply that they're accurate so they sound more like live music the closer they get to the volume of live music.  Other speakers are less dynamically accurate but sound subjectively better at low volume.  

I wonder if there is a relationship between the ability to handle high volume and better sound at high volume.  What speakers sound great at low volume but can handle high volume? 
What speakers sound great at low volume but can handle high volume?

The company founder/chief engineer (driver inventor) Billy Woodman had a specific target in mind back in the 70s and 80s: the wide dynamics of American speakers (JBLs, Altecs, etc) and the high resolution of British speakers (Quad, 70’s era KEF). The fault of many of these earlier American speakers is they played loud but sounded awful. Inversely many of the British speakers had great sound quality but would not play loud enough for rock and roll.

So I can tell you for a fact that one of the biggest attributes studio buyers hunt for is consistent sound at any SPL. This is what ATC always shoots for, how to maintain performance at all operating levels. 

At home we need it to sound good at very low levels.  In the studio we need very high levels to at least approximate the performance SPL in the tracking room.  Mixers cannot work at high levels all the time, so they need the speaker to be loud for the artist to hear it back when they want, but sound just the same at low level when you need to work with a microscope to hunt down errors.