Everything has a sound signature, yes, but many are so close that the differences are imperceptible. And many more are perceptible, but only with very close, volume matched, eye squinting concentration. The only differences that are worth pursuing, IMO, are the big, obvious differences - and those, more often than not, are a matter of taste rather than superiority.
When I was going through my HiFiMAN phase, I remember discussing the "synergy" of finding an amp that helps the HE-500 "scale up." Members wanted to beef up the bass to LCD-2 levels, or increase the micro detail, etc. I couldnt help but think that instead of searching endlessly for upstream components that made the HiFiMAN's "sing," maybe they should just find another headphone that sings all by itself. For me, that headphone is the HD800.
So I have no issue with plugging my $1500 headphones into a $400 amplifier. Of course others will disagree, but for me, there's no more pleasure or performance to be had by spending mor