Thiel 2.7 VS 3.7???

Seems to me that you have both enough room and amplification for the 3.7s. I agree with Vhiner about the sub, the Thiel sub would be the way to go if you take that choice.

Since no one has mentioned it yet, again I'll venture a guess based on my past experience with the Thiel CS2 and CS 3.5 (as well, frankly, as in the cases of other speaker lines, like Dunlavy, when you went up the line to larger speakers), and see if anyone else can chime in. The big differences in the past between the two classes of speakers to my ears were both in bass quantity and quality and, more importantly, a better sense of ease in presentation from the bigger speaker and an overall bigger sound. The drivers moved more air, weren't working as hard and overall had a more relaxed and open sound, less strained. I know the 2.7 is really light years ahead of the CS2 and is probably one of the best Thiel speakers, but the 3.7 is a good deal better than the original CS 3.5, much as I liked that speaker, and is very highly regarded. I would think that ease, particularly in loud and complex musical passages, would be noticeable--it certainly was to me. If you listen more to smaller scale ensembles and music and at moderate volume levels, it may not be as important a difference. Just a guess based on past experience--I'm hoping someone who owns or has compared the actual speakers will add their two cents.

Well said Rcprince, that is exactly how the larger CS6 plays in my room versus my 3.6. Moving more air with more ease and more relaxed when pushed through a complex passage.

The 3.6 is an excellent speaker, I like to compare it a car going down the freeway at 80 mph - with the 3.6 you feel like your going 80 with the CS6 you feel like your going 50. That is what you get with a larger speaker.

I completely agree with the Rcprince and Pops! The bigger more expensive speakers are more dynamic (sometimes dramatically so) and play with much greater ease doing so.
I usually expect deeper bass response with those kind price increases though, and I don't think Thiel really succeeded in that regard all the time.

Unsound,

Yes that is exactly what I am talking about in this case. Since they share the same mid/tweeter driver & cabinet is more similar than not, I am not sure the jump for 2hz is worth it if that is all there is? (mostly)

That is the 12k question! I have never heard the 2.7 although I am sure i would love because I am a Thiel guy. I have come so close so many times to buying the 3.7, have heard it extensively at 2 separate showrooms with various components and could just never commit. The same reason Unsound mentioned above with the CS6, just such a big price jump for what I perceived to not be worth it compared to my 3.6. They sound great no doubt but for me to spend that much on a speaker I am hoping that will ride me off into the sunset. And I didn't get that during my time with them.

I would rather stretch a little further and find a speaker that would, that is why I am disappointed Thiel has no plans for a new statement speaker. I was sort of holding out for that! Sounds like you have some similar reservations. You might be better off staying pat, tough call.