I have the Thiel 3.6's and their low sensitivity and low 2.5 to 3 ohm impedance makes it a challenge for a tube amp -- but the one saving grace is the impedance is flat throughout most of the frequency range. Tough to find an excellent high power tube amp with speaker protection without spending a fortune.
I ended up designing and building my own tube amp using the KT150 tube in ultralinear and triode. For speaker protection, I used a circuit breaker power switch tripped by high plate current from tube failure, loss of fixed bias or speaker terminal short, plus a time delay heater warm up. I had a custom single tap 3-ohm output transformer rated at 70 watts (down to 27hz) wound by Jack Elliano at ElectraPrint. The amp uses balanced inputs only, with no phase splitters -- just a pair of 6SL7 mu-followers to swing the signal to the output tubes. Works extremely well with the 3.6's doing a decent job at the low frequencies and the overall dynamics preserved. I still use the Mark Levinsons when power is called for but for a lot of softer music the 60 watt KT150's fit the bill much much better