To try to recreate the Magister experience I hooked up the Magnums to the little ECL86 amp mentioned previously. I was greeted again with enormous deep bass, but not as happy over all, a rather lumpy frequency response, and a big question, what's going on... So I hooked up my Hybrid amp and the Magnums sounded a bit more normal, but the bass was considerably reigned in, disappointingly.
I think the Magnums like being back against the wall, they seem happy there and the in room response is now quite civilised with a nice boom free sound and bass is only there when it should be.
Still confused, had the ECL86 on the bench to measure to try and find out what's up. The frequency response looks a bit rolled off to the bottom, so no help there, but the treble peak is looking quite promising, explaining the "prominent" treble. After some wriggling the little amp surrendered its output impedance, all be it with significant 50Hz artefacts.