Haven’t heard the Gustard R2R but reviews are off the charts. That’s where I would go. I have a Musician Aquarius and if it’s anywhere near that and by all accounts it is (possibly better) could be a steal. It’s a business obviously so prices will go up IMO in the near future if that’s the case.
+1 on the Black Ice / Jolida tube dac. Great dac, very musical and can even be had used for well under $500. Wish I still had it to compare.