Do upgraded LAN cables/purifiers/switch box make a difference. What is recommended, if so?

"Do upgraded LAN cables/purifiers/switch box make a difference."

IME, little to none.  This stuff seems to go through a life-cycle starting with early adopter fervor, leading to a bandwagon of vocal supporters, and then the inevitable manufacturer's upgrade to the new de rigueur version of the same thing.  The cycle keeps going as long as people keep buying.

In my world of streaming through Roon, changing/upgrading DACs has made the most improvement to the sound of my digital front end, followed by upgrading streamers.  The server has surprising made little difference (assuming separate server and streamer).  I do like using linear power supplies on everything, but I couldn't swear that I hear a difference.  The rest of it, including cables, filters, purifiers, switches, optical lines, etc., even though I still use some of those, have made little (imaginary?) sonic difference in my system.  YMMV

Everything makes a difference. You have to experiment with different tweaks. I have isolation, as well as different filters throughout my entire audio system, including my speakers. Yes tweaks are a critical part of my audio system. Happy listening.

The answer is Yes. Check out Silent Angel.  They have some really great products and would further educvate you on the possibilities of sound improvement.  I understand that some of these options may be above your range.

Just to circle back, I agree with others to focus on the DAC first before tweaks (although the $40 NetGear switch isn’t too painful to try), and the streamer would likely make a significant improvement as well.  Not sure what your power situation is, but if you’re concerned with a lower noise floor you should budget for a good power conditioner as that will benefit your entire system and not just the digital side.  This one has gotten some really nice feedback from people here and is relatively not too expensive — just something else to consider FWIW.

https://www.kinki-studio.com/product-page/kinki-studio-x-vinshine-audio-tai-hang

I bought a trendnet 8 port unmanaged 1g switch for around $20 on amazon and I was surprised not only by it not harming the anything but it actually reduced a bit of noise. More natural sound. I have nice Ethernet cables and yes they make a difference.