Bondi, I agree that the S and Q are fairly different sounding as you found. I do like the S5 Mk2 much more than the Mk1. I have heard the Q3 and both S5s in four or five systems, but never in the same system at the same session. The Mk2 and Q3 would be an interesting direct comparison in the same system. I will say that I own the Q3 and did not consider the S5 mk2 based on my auditions, cost, and aesthetics. I think they are both excellent, but they appeal to different tastes.
Smodtactical, If I were both able and willing to spend $50K, I would certainly consider the M2 or a used M3 along with the S5 Mk2. I suspect they all sound slightly different from each other and certainly different from the others on your list.
Buying speakers is a very personal choice based on many factors. I encourage you to listen to as many of the speakers on your list as possible with your own music in well set up systems. Take your time making a careful and deliberate choice. Good luck and enjoy the process.