Ultra high resolution

Hi folks, I suppose this is a question none could answer appropriately. How come that some (there are to my knowledge only two of them) amplifier brands are building such ultra high resolution solid state amplifiers without having a treble that sounds shrill or piercing or artificial? It is of course proprietary info if you ask those manufacturers.
Is it because of very tight selection of matched transistors? Is it because lack of global but high level of local feedback? Is it because of the use of very expensive military grade parts? Is it because of the power supply? Is it because of the application of special circuit design? Is it because all of the above?

Chris