Phd, FWIW, I have horns too and no worries on the top end. However, I can't listen to passive volume controls in my system- they come off too bright and no bass relative to my preamp.
Also, generally speaking horn speakers don't play well with transistors; the reason being that horns are often highly reactive and present a lot of back EMF to the amplifier. If the amplifier employs negative feedback, unless the designer really did his homework to prevent radio frequencies from entering the amp through the feedback network, that and the back EMF will really cause the amp to be shrill.
This is one reason you find most horn installations using tubes.
Also, generally speaking horn speakers don't play well with transistors; the reason being that horns are often highly reactive and present a lot of back EMF to the amplifier. If the amplifier employs negative feedback, unless the designer really did his homework to prevent radio frequencies from entering the amp through the feedback network, that and the back EMF will really cause the amp to be shrill.
This is one reason you find most horn installations using tubes.