DAC with i2S

A used PS Audio Directstream MKI. Then once funds allow, upgrade the transformers to APS along with the Vocm mods. Complete sleeper dac. I cannot imagine anything under $20K sounding better.

Musetec 005 at $3k though the USB input maybe the best of the input options. Used can maybe found under $2k. Excellent DAC for the price. Wish I still had it.

I own the Musician Pegasus that’s excellent and can be had for $1100.  Here’s a good review…

https://soundnews.net/sources/dacs/musician-audio-pegasus-r2r-dac-review/

For that price you could add their Pisces DDC for $520 so for $1620 total you’d have a complete i2S setup 

https://aoshida-audio.com/products/musician-pisces-ii

Incidentally, I added a used Denafrips Iris DDC to get i2S with my Pegasus and the improvement over SPDIF was not small and very well worth it.  Hope this helps, and best of luck.

Gustard R26 is a well reviewed Dac.