thielliste,
Yeah, the Thiels seem to perform well with tubes IMO.
As to SS, from my experience I can only say that 250W of Bryston power drove some Thiel CS6s that I had very easily. The 3.7s should be even easier to drive.
If one has a really big room and listens really loud, that could change. But then, moving between 250 W to 300, or even 140w to 300, is a very modest increase in actual available loudness potential.