FWIW, I sure don't hear any harshness in my Thiel 2.7s driven by my conrad johnson premier 12 tube amps :-)
Not anywhere, not a bit. They are one of the smoothest sounding speakers (at least with this amp combo) that I've ever heard.
And the sound is big, rich and lush - not the usual descriptors that have been traditionally associated with Thiel speakers (in the mind of many audiophiles).