Thiel CS5i's VS other Thiel Lines

All:

I am a considering a purchase of a pair of used but extremely well taken care of Thiel CS5i's from a friend and audiophile on the west coast and would like to get the opinions of this group. In particular, I'd like to hear from those who have had experience with Thiel products and might be able to compare the relative merits of the Thiel 5Si's with the Thiel 7.2's, Thiel 6's and Thiel 3.6's. Any and all input from sound quality, applications, strengths/weaknesses would be greatly appreciated.

Tim