@willemj
I haven't looked at the Stereophile measurements and honestly don't need to. I have owned ARC amps, VTL and Ayre and neither have provided my Magnepan 20.7's 87db with the musical pleasures of my PrimaLuna Dialogue Premium HP amps. To the point that I sold/ traded my ARC REF 5SE, DS450M's and ARC REF110 for the PrimaLuna preamp and amp. If you are ever in Seattle come to my house and take a listen and become a believer. And I would bet that if my PL can drive my 20.7's they can handle any Harbeth speaker.
Cheers