Stereophile also raved about the Holo Spring. I owned the Kitsune Spring for a while and thought it sounded awful, so I'm not giving any more credibility to this review.
HoloAudio May Dac, New King of dacs? Stereophiles review on it?
Could be, got a very good review and bench test.
And yes it’s R2R!! and only $5k (wish it had a volume control though)
https://www.stereophile.com/content/holoaudio-may-level-3-da-processor
Cheers George