I dont see why I would want to use neutral amplifier to be honest...
No headphone is perfect - that is why I WANT to use a colored amp/DAC...
Lets take the HD800,yes it is treble heavy, yes the bass is less prominent, but that is exactly why you want to use that slightly colored amp to boost certain areas and tame other ones... IMO there is no "perfect" headphone and that is when colored, whether tube or SS amps come into play.
Other than that 




















