Value of a premium Ethernet cable

+2 on the LinkUp cable recommendation. I wouldn’t hesitate to run it from the router to switch, with the short run after the switch using a better cable or even LinkUp into streamer. Should be an improvement over the cheap cable.
Add Purist Audio Design CAT7 to the list as well for the short run into streamer.

I use and like the Network Acoustics Eno streaming system (passive filter and cable). It made a nice improvement in my system. 

Buy with a solid return policy though. If you don’t hear any improvement (unlikely) or don’t like the change in sound, you should be able to return. 

Consider changing the long run of ethernet cable to fibre from the Etheregen.

I’d suggest putting the Etherregen as close as you can to the server. Keeping the clean side cable as short as poss. really matters. If anything, use fibre for a long link between router and Etherregen

Thanks to all who responded.

soix:  We have a (Google) mesh network in the house but most places I've read say Ethernet is preferable.

antigrunge2:  I've ordered one of those cables for the short run between the EtherRegen and ROCK server. Certainly worth a try!

gdnrbob  Excellent idea; I'll check out HiFiShark. Didn't know about that site.

jerrybj:  Running fiber to the streamer presents the same logistics problems as the long ethernet run, which I can handle, but would also necessitate an FMC near the streamer, with either a wall wart power supply or another linear power supply.

audphile1:  I'll check out Network Acoustics Eno; that's a new one on me.

If anyone's interested, here's the setup in the hallway outside my listening room.

@john_g 

You are lucky you get to use a hallway. Jealousy abounds.