Ethernet

Agree with many here that Blue Jeans would be more than fine for setting a baseline to start.

I'd then start trying different eth cables from the splitter to your streamer and vault.

I have a similar setup today:

Router > Switch > Streamer

I had all blue jeans, but now I only use blue jeans of about 12 feet from Router to Switch (LHY SW-6), and then a 1.5m Sablon eth cable to the streamer.  In my system, it's an upgrade in SQ.

The Avanti cable recommended by akg above looks compelling.  Give it a try.

Can you provide more details on what the "splitter" is?  Is it a switch or hub, or something else?

Blue Jeans is what you want. Anything over is a scam. Ask yourself - does Amazon (Tidal, etc) use $1000 Ethernet cables in their data centers? No? Why would you?

@mikhailark 

audio isn’t digital since analogue noise messes with the subsequent D/A signal conversion; i.e. RMI/EFI or ground level noise matter in audio, not digital.

@antigrunge2 - where does it mess with USB and how? SPDIF - sure. This is why no one should be using coax. I am yet to hear explanation on USB. Ethernet even more resilient. Everything is retransmitted if there is an error. Again - your email does not change no matter fiber, electrical, satellite links and 100 times conversion of electric to optical to radio and back. It comes to you 100%. So is the FLAC file.

o2

+1 for Supra Cat 8+ cables, been using them for a while; and a terrific value (and really good performer)......all of their cables are good performance for the money. As mentioned, they are made in Sweden to very high quality.....and are lesser known in the US.

The official distributor for the US sells on eBay under the name sjofn HiFi, it's legit purchase. They have lengths from .5 meter up to 30 meters