Reducing my digital noise floor.

Ethernet is just, as you said, "data" and there is no "quality" to it (data is data).  This data is likely bit perfect (checksum is verified), or we would have a lot of problems everywhere.  The only thing you can improve, IMHO, is amount of noise being injected from outside.  Ethernet standard has inherent isolation (transformer or optical), but rejection of common mode noise is never perfect.  Use Ethernet cable, as short as possible, with good shielding (but you already do).  Line filter would help in any system, but you already have that.  Your setup is as good as it can be and I don't know what else to do to improve it.  Ethernet speed is irrelevant, since it is not a real time transmission. Data comes in packets at different, than D/A conversion, rate and as long as you don't have missing data (gaps) quality will be the same.  

Check out uptone audio Etherregen, I use one and recommend it, although it does take about a week to burn in.

Lots of threads over on computer audiophile , you can try it on a 30 day return.

i use wifi to my computer then auirvana-tidal via usb to dac...
all me wee bits are perfect
no danglers
quiet as meeses

You could try placing a fiber media converter with SPF module at your router outlet. If your streamer has a fiber network connection, you’d connect a fiber cable between the SPF and streamer. If streamer only has ethernet port, you’d have to add another FMC/SPF connection to convert back to wire.

I have two FMCs and it works well, but I can’t say it’s a significant difference over just straight ethernet cable.

Have you tried RENDU?From small green computer?

I have recently inserted Network Acoustics ENO Ethernet Filter between my router and very happy with the results. It’s probably the best ‘passive’ device out there that effectively lowers the noise floor within ethernet router and switches. I bought the Ag version package with LAN Ag cable.
https://www.networkacoustics.com/product/eno-ethernet-filter-ag-695-incl-vat/

Give it a try, it comes with 30 days return policy.

ENO
Hand wound EMI chokes made from OCC wire for the CU version.
Trial period.

Thank you for taking the time to respond and the insights, some things to consider. As I choose a direction, I will be sure to follow up.

M