I also have a Lumin U2 streamer together with an English Electric8 switch. I use high quality Cat6 wiring from my cable modem to my Luxul AV router and then to the EE8. Finally, I use a Shunyata Sigma Ethernet cable from the EE8 to my Lumin U2. My DAC is a Bricasti M21. A DH Labs Mirage USB cable connects the U2 to the M21. Power to these components is conditioned by a Shunyata Denali and delivered via Shunyata Venom power cables. I think the music I stream (using either the onboard Lumin app or my Roon Nucleus+) from Qobuz and Tidal sounds rather good.
That said, I also have a Bricasti M19 SACD transport, which employs an I2S connection (using a proprietary cable supplied by Bricasti). The power conditioning and cable are the same Shunyatas. More often than not, using what I try to ensure is the same recording as I am streaming, the SACD or CD version sounds even better — greater clarity, better imaging, wider/deeper soundstage, and more dynamic.
I cannot explain why exactly, but I suspect that the far, far shorter and less complicated data path of the CD/SACD may be the reason.

