Thieliste, my advice is to wait for the 7.2 if that is the speaker you truly want. I own the CS6 and 3.6 and love both speakers. While they are cut from the same sonic cloth I ultimately prefer the 3.6. The CS6 is slightly more dynamic, able to play louder with no strain, the 3.6 is more transparent. They are the most transparent box speaker I have ever heard. I also slightly prefer the tone and timbre on the 3.6. I could live with either and that is why I have both.
I think the difference in the design makes them sound slightly different. I am not sure I am a fan of the coaxial tweeter/midrange on the newer Thiels which both the CS6 and 7.2 have. Richard Hardesty has an interesting review on the 6 and actually prefers it over the 7.2. The 6 is his favorite Thiel speaker, it is an interesting read.
One thing for sure, the CS6 and especially the 3.6 are great bargains on the used market, so if you decide to go with the CS6 you will not be out a huge investment. BTW, you have great speakers in the 3.7. Good luck with your decision - can never have too many Thiels!