I had similar results with my Nord Acoustics Hypex NC500 based amps paired with my Martin Logans. When I first got them they were a significant upgrade from the older class D amps I had in before. They were very controlled and detailed with a low noise floor, but I found them harsh at times and fatiguing at high volumes. I upgraded again to the PS Audio BHK300s - not a fair fight, as these are much more expensive amps, but the hybrid tube/ss amps resolved the brightness and fatigue I was experiencing with the Hypex ones when paired with my electrostats, and I lost none of the detail (though my noise floor did go up).
The focal sopras were my 2nd-most favorite speakers when I was demoing last year, but the Martin Logan Expression 13As just imaged sooooo well when set up right, and now that they are paired with better amps, I'm very happy.
The focal sopras were my 2nd-most favorite speakers when I was demoing last year, but the Martin Logan Expression 13As just imaged sooooo well when set up right, and now that they are paired with better amps, I'm very happy.