Standmount speakers. I have $5000.

I would back some of the early recs for the Dynaudio Special 40’s. I am in the process of replacing my ATC SCM 19’s, which I am surprised have not been mentioned on this thread and which I suggest you listen to, with them. They are just very magical, cohesive and musical with a huge 3 dimensional sound. (They aren’t as neutral = analytical? ... which is fine with me)

You mention 3 drivers instead of 2, but the simple and wide first-order crossover/integration of the 2 drivers in the S40’s is something else and they often give the illusion of large scale floorstanders more than any other standmount I have heard. Low sensitivity notwithstanding, the Dynaudio’s won’t fall apart when going loud. WAF should be good with the grey birch finish as well.

I have not heard the C20’s yet and they might be a step up in terms of refinement and bass depth (which you have covered with your subs), but from what I have read at the possible loss of some of the magic that the S40’s have.

I like the Monitor Audio Gold 100. The new model is fantastic in my opinion. I have the old model and just love them. My room is about the same size as yours. Also, Monitor Audio Platinum PL100 

If I had $5000 to throw at a pair of stand mount speakers, I’d probably be looking at Fritz these days. Spartan looks but top notch build qualty and will mate better than most with most any amp including tube amps  plus probably a fair amount of change to spare with $5000.

I do keep looking at them at least anyhow.....

If you want to go hog wild, check out JWM Acoustics for superb (large) stand-mounts, and over-the-top WAF.

I'm surprised no one has mentioned Egglestonworks Emmas; I heard them last month at T.H.E. show, where they were selling for $5500.  Best speakers I heard under $10K.