I started with Fibre Optic converters similar to what’s shown on the Green Computer website but ftom amazon and much cheaper (looks like it’s the crap). That did improve some things and it gave me a taste of what’s possible.
I started this post to get some more thoughts on the subject.
The fibre optic media converters lowered the noise floor but also thinned out the presentation and imparted this slight dryness in the midrange. In a long run I couldn’t live with it. So I gave the Network Acoustics Eno a try and am really enjoying it. As @lalitk pointed out, smooth and natural presentation.
I heard the EtherREGEN is also solid. But I kind of dig the Eno - no power supply to worry about, no power wires to run.

Ultimately, only trying this in your system will show wether or not you like one network filter or switch over another. 

FWIW, I used to own a Sonore opticalRendu which was using fiber optic conversion. It was really good, but my current combination of Eno + Innuos Zenith is more natural sounding as @lalitk mentioned in his post. I don't think optical is best by default -- like most things it depends on the rest of your system and preferences.

My experience has been both up and down with ethernet and optical, I agree, depends on implementation. At this point I prefer optical post server, ethernet pre server. I did try generic FMC prior to server, heard presentation similar to audphile1, also heard similar presentation adding audiophile switch prior to server. At this point prefer my router powered with lps direct to server vs. either of those two solutions. Network Acoustics Muon filter will be my  attempt at lowering noise pre server. Post server I prefer optical via generic FMC,( soon to be Sonore OpticalModule), and Sonore OpticalRendu. This streamer much preferred to prior SOTM SMS 200Neo.

I think optical gets criticized mostly because of these generic FMC, they have pretty poor clocking and noisy power supplies. Not to say they're not helpful, they are in many cases, but one can do better with optimized optical.

+1 @lalitk

I also found good ethernet cables (in/out of a ethetregen) better than using optical from a switch or out from the ethetregen. With my gear optical was too sterile.

Room and the other usual factors make up the rest.

Any comments on this: DXE-ISO-PLUS-2 for filtering?