Hackmaster, I don't think the newest Thiel's speakers impedance load is that much different than his other recent entries. They are more sensitive. Some of Thiels older models were more tube friendly, particularly the CS-2's with a 6 Ohm nominal, 5 Ohm minimal load and The 3.5's that were 4 Ohms nominal , 4 Ohms minimal load. The 3.5's did require a beefy tube amp due to the use of an active equalizer. While Thiels recommended at least 50 watts that rating was in reference to standard quality solid state ratings where the amps would double down. As such one would need a tube amp with double that rating from it's appropriate tap. These impedance loads were very steady compared to most other speakers. Unfortunately high powered tube amps usually(!) cost more that similarly powered solid state amps. Most amps enjoy the freedom from roller coaster demands that steady loads provide. The point being that it's not that all Thiels have been unwilling to work with tubes, it was just usually more expensive to do right.