John Curl’s Halo JC1’s mono’s all day every day, especially in high-bias mode, and especially when driving harder loads.
As the JC1’s are Bi-polar (BJT) output devices, which far out perform (when the going gets hard) the Mosfets which I believe Plinius use.
The XRT 28 are stated as 4ohms nominal, so you can bet your life that somewhere they’ll drop to 2ohms, and that’s without taking -phase angles into account. That’s when you want bi-polar (bjt) outputs on your amp, naturally the rest of the amp has to be good also which the JC1’s are definitely.
Cheers George