I don't have a 1.3 SE but a 1.3 MK II, I don't know how much power the Musical Fidelity puts out but remember the 1.3 SEs like all Dynaudio speakers needs lots of clean power to sound their best.
If you are hearing sibilance it could either be lack of power or some of your upstream components are inherently bright, and you're finally hearing them from a ruthlessly revealing pair of speakers.
If you are hearing sibilance it could either be lack of power or some of your upstream components are inherently bright, and you're finally hearing them from a ruthlessly revealing pair of speakers.