All I’m talking about is the OP’s Thiel CS5’ speakers and today’s similar speakers like nearly all Wilson Alexia ect ect and what will drive them the very best into those varying low impedance’s they have.
And that would be one of the linear bjt output brutes, with a power supply big enough that can power Lower Manhattan, ( read that in Stereophile somewhere sounded good).
And no Class-D I know could as do it as well not even the 3000w!!! Behringer.
The old Mark Levinson ML2 (BJT monoblocks) at just 25w would slay it for sound quality and control "to a given volume".
https://ibb.co/X5rfnXL
Cheers George