Hello, chiming in to share my experience with this jewel. After few years of happiness with driving HE560 with Gustard's exceptional H10 amp, feeding it by iRDAC, I've got an upgraditis gravis and ordered new almost everything. I am waiting for Gustard's new X20U-Pro dac, having balanced interconnection ready to pump it in into Cayin iHa-6. My balanced headphone cable being still on its way to me, I am driving Hifiman golden mid-class HE560 with Cayin via single ended cable, and I am hearing what I haven't heard before.
I am not very poetic in nature, never been good with the terms like warm, analytical, congested, etc. What I hear is clean, dynamic and energized, and I like it very much. I really enjoy that even without critical listening I can hear new details I havent heard on the same setup (Arcam iRDAC and Hifiman's HE560) before. I also found out that the music really plays around me for the first time. I am to lazy to imagine and pinpoint instruments in the space, however now I feel really surrounded by the music, not just feeling like being stereoed.
My only worry is occasional sibilance. Being in love with what I hear, I tend to blame the records, however in case of e.g. Queen's "Under pressure" from the 2012 SACD, where especially the first verses the "sss" are piercing my ears almost painfully, it is hard to blame poor mastering (at least I think so, please feel free to help me see the light
).
Otherwise, I am really enjoying this headamp, and looking forward to complement it with Gustard's new juggernaut DAC and fully balanced interconnect. And who knows, maybe I will help myself to an old set of HE-6, being able to finally power them properly...