I’ve owned a Selekt (not Surround) and I currently I own two recent Klimax. Some comments:
I’ve discussed Cat 7 with network engineers, including my Linn dealer (who used to be one for a major hardware company before going into audio), and they think it’s a bad choice for this application, because of shielding incompatibilities with domestic gear.
I’ve heard a definite improvement when I replaced a GS105 upstream of Klimax with these.
I got a further minor improvement when I replaced Cat 6 between those switches and Klimax with optical.
It could well be that USB from HS-264 is just electrically less noisy than your current Ethernet. The bits are not different, but the stray EM junk coming along with them down the wire can matter.
In all of the above, the issue is not the bits themselves, but keeping stray EM interference away from Linn gear. For some reason, the GS105 is a worse electrical noise source than that discontinued Cisco switch.
This is entirely about application. With this hardware USB sounds better than Ethernet. With other hardware the opposite is being observed (Gustard R26). There is no hard and fast rule as to what sounds best. Look at where your manufacturer has made the effort and you will probably see benefits.
I would also recommend installing a Tp-Link MC200CM Gigabit SFP to RJ45 Fiber Ethernet Converter (or something similar) after the Netgear switch, fiber ethernet, then another Tp-Link MC200CM Gigabit SFP to RJ45 Fiber Ethernet Converter back to wired ethernet into your streamer.
The noise from the router, Roon Core and switch gets dropped completely by the fiber, leaving only the short run of wired ethernet to the streamer/DAC to pick up noise. Make those cables (wired ethernet to streamer and USB to DAC) as short and as high quality as possible.
Next step after that is investing in good linear power supplies, quality FEMTO clocks, and an “audiophile” switch.
You will hear a difference.
I use a good quality gaming Router (ASUS), a Paul Pang Quad Switch, iFi Zen Streamer with power supply, and from there into my DAC, with the highest quality Audioquest cables I can afford. I am incredibly happy with the sound and pitch-black background.