Best Server To Run Roon Core

I was just going by what the ENO manufacturer says on their website:

"A unique (patent pending) passive filtering system which plugs in between your network switch or router, and your streaming device."

AFAIK, EtherRegen is not passive but I could be wrong. Either way, I'd go with what the creator of the product recommends before experimenting with a different setup.

In @decathlon1991 's case, the Nucleus is not the streamer. It is another source of data. I think the primary goal is to remove any noise on the ethernet signal before it reaches the streamer, and this includes noise introduced by the Roon core. 

But it's worth trying it in both locations to see what works best. 

@  decathlon1991
Your question : " So my question is will the ENO Ethernet Filter Ag or the EtherRegen be placed from the Router to the Roon Nucleus or from the the Roon Nucleus to the Cary? "

I use the EtherRegen immediately in front of the streamer(s).

If you have a streamer and a server (two separate units): put the first good Ethernet Switch or Filter in front of the streamer. If you have two of these Switches or Filters.... well, you know what to do.

Honestly you don't need to spend huge $ on a Roon Core platform. Most of these devices people are recommending are for use with USB direct connection, if that is your intended use then by all means spend the cash. But if all you want is the ability to try Roon build yourself a Rpi 3 or 4 with an allo digione hat, install OS of choice with RAAT roon endpoint and run core via ethernet from an old pc/mac if you have one. Cheapest way to get Roon integrated into your audio system. Running this over your network via ethernet doesn't have the isolation issues you find running the core platform directly via USB.