Concentra II - Power

Has anyone tried running this amp on some tough to drive speakers like Maggies? If so, how did it do?
JR runs very good with Dynas. I have every tried Concentra II with Dyna 1.3SE, 1.8mk2, 25 Special. All works fine.
My Concentra II drives a pair of Celestion Kingstons which are 84 db efficient. I have used many different amps (ARC, Bryston, CJ, Aaragon) over the years with these speakers and the Concentra II drives them very well with non of the compression or muddy bottom end that some of the other amps showed under certain situations..