After setting up my speaker system, I must admit that the difference in performance among DACs does not justify the huge cost differences, in most headphone setups. But the difference in imaging and instrument positioning became very prominent when connected to my current speaker system, in an 300 sq. ft. room, to the point that my Zodiac Gold and Weiss DAC202 have gone back to my bedroom and study, respectively, for my headphone setups, and leave my main system in the living room for good.
My Esoteric K-01 truly shines in the speaker setup (for details, see my signature block), in both details retrievel and placement of those details, as well as overall imaging, Y axis depth and instrument positioning. IMO, these are the attributes that sets the high end DACs apart from the mid tier ones. My Weiss DAC202 and Zodiac Gold just cannot cut it when the scale of things got much larger. While you can detect some kind of positioning and the Zodiac Gold is still acceptable in terms of instrument positioning, the sound stage is very 2D and lacks depth when compared with the Esoteric.
But frankly, except maybe with the Smyth Realizer and SR009, I don't think the high end DACs' price is justified for any headphone setup, especially after comparison with my Antelope Zodiac Gold and Weiss DAC202. And with the LCD2/3, the difference is so small that it is not even worth it. Based on my experience, I would recommend Head-fiers to refrain from upgrading their sources beyond mid-tier DACs like Zodiac Gold, Weiss DAC202, Resolution Cantata, Berkeley Alpha, PS Audio DAC, unless you are using the true high end DAC for either of the following two purposes:
(1) A full speaker system in a reasonably sized room
(2) A Smyth Realizer with a Stax SR009 (or maybe 007) setup