I had Roon Core on two different generations of mac mini. Currently have Roon Nucleus One. It’s been great. Both sonically and functionally. It responds well to better Ethernet cables.
Your SGC should be fine.
Can you describe the attributes of streaming that factored into your conclusion of it sounding inferior than the local files? What characteristics set one apart from another?
I’ve experienced the same exact issue and resolved it by upgrading the streamer. But my cables were in order. Yours aren’t.

