The Matrix X+SPDIF 2 was one of the first. If your DAC makes the i2s interface sound better you would probably get better SQ with a different DAC.
DDC Comparisons
anyone compared the Denfrips Iris 12th to the Gustard U18?
what else is out there in this price range?
I'm looking taking advantage of the better sound quality of I2S and sending my external clock signal to the DDC, which will then in turn send the clock signal to my DAC (Gustard X26 Pro) via HDMI
or maybe I should just upgrade my DAC.....