I've optimized every single thing in my streaming setup from modem to dac, every single piece of equipment (each piece has been comparison tested vs others) using lps, top flight cabling (also comparison tested) which means ethernet, optical usb, I2S, DC, AC, AC conditioning. I have optical conversion via Sonore OM, OR, AfterDark optical cabling, Finisar 1475 transceivers. Custom build streamer using all the best ATX build components, also includes JCAT Netcard XE powered by Uptone JS-2 choke based lps, streamer itself powered by JCAT Optimo ATX, a $6k lps, running Euphony OS, which means 7 cores running below 1% of resources virtually all the time, this with Roon core. Low latency name of the game here. And so I have all bases covered, usb streamer is top notch, 006 usb top notch. And still my I2S setup provides meaningful improvement vs usb.
And it only continues to improve with burn in time. Got tired of dealing with inconsistent performance so ran Gaia, Tubulus Ximius 24/7 for a week, New power cord on space heater for a week. Gaia now on much better isolation platform with Stillpoint footers. Result is presentation even more relaxed, refined, flows exactly like my very nice vinyl setup (think I have more money into it vs digital). And resolution/transparency up a notch, performers in room effect has been there for some time, now reach out and touch imaging. Based on my own experience with my own digital, and my memory of both other in home and audio show digital, this is best digital I've ever heard, right up there with best vinyl setups ever heard.
So bottom line, I agree every single aspect of streaming chain needs to be optimized, no ddc, I2S cable alone is going to extract max potential from any dac, its an added benefit. The most important added benefit I expect the Gaia is providing is the OXCO clock and power supply to that clock, the diminished jitter provides this new level of ease and refinement. I also suspect usb is being further optimized even after the OpticalRendu's optimization?