Tube amp for Thiel CS1.5s

First you should get a picture of the Thiel's impedance curve. If it goes all over the place, avoid using tubes.
I believe that Thiel's are VERY power hungry. Try Bryston 4B-ST or McCormack -you might be suprised! Solid state amps these days are radically good! I use ARC VT-100 Mk-I with KEF Ref 3.2's. The KEF's have a purposely flattened inpedance and work extremely well with the ARC. I had been using Audio Artistry Dvoraks with mixed results. I auditioned some BEL MK-V's (soild state) and the Dvoraks were transformed! You really have to work to achieve a great sounding system.

Abecollins: You are right. Per the archived review on Stereophile's website, the 1.5's do not need tons of power but likewise will not play super loud or display extreme dynamics. If one has a small room, this should not be an issue. The review also states that the 1.5's have a very flat "resistor like" impedance (@ 4 ohms) which tube amps love. My peception (about power requirements) probably biased by the unusually small mid drivers in the later Theil designs. You're NOT going to get a huge healty sound out of a teeny (4 inch in 2.2?) midrange driver without plenty of juice!