Your journey to separate Streamer mirrors my own.
I was an early user of the ZEN Stream, and was impressed by this little unit. I have a DAC that offers I2S and I really wanted that, so I bought the Matrix X-SPDIF 2 USB Interface with I2S. I used that between the ZEN Stream and my DAC and got another level of clarity with that.
I have now moved on to the Musica Pristina A Capella III which is a dedicated Streamer with native I2S outputs. Astonishing upgrade! Everything improved, including lower noise floor, crystal clarity and certified Roon Ready support.
Talk to Kevin a Musica Pristina. He is easy to work with, and incredibly knowledgeable.