Ethernet source

I'm trying, somewhat desparetely, to improve the sound quality of streaming which presently I wouldn't even say is up to cd quality, even though I,ve been streaming hi-res files on qobuz.  My streaming device is a Sonore ultrarendu.  I,m limited in terms of Ethernet access where my system is located.  I,ve been using a net gear power line device to obtain Ethernet off of 120v circuitry.  There is, however,
an Ethernet port on my tv cable box.  Would I be better off using that as opposed to the net gear?

Couple of things to do to elevate SQ of your Sonore ultrarendu,

1. Linear Power Supply, if you’re using a wall wart.
2. Clean Ethernet Feed
3. High Quality Ethernet LAN cable

Get rid of Netgear power line device, that is absolutely one of the worst thing ever invented. Get a Google Wi-Fi Mesh Network system,

Plug one of these directly into your internet provider’s modem or gateway to create your Wi‑Fi network. Connect the ultrarendu into 2nd Google Wifi point.

The Ethernet port on your cable box is a ‘input’ port so you cannot use that to feed ultrarendu.

Use a high quality LAN cables like Supra CAT 8.

Couple of big pluses of Google Wifi System, WiFi is much more robust than the basic modem provided by your Internet provider. Mine is AT&T and the WiFi coverage simply sucks. Secondly, you can prioritize the WiFI traffic to a device in Google WiFi app based on a usage.
Ethernet (without using power lines) is best. Wifi after that and power line is absolute last.  I believe the Ethernet jack on your cable box is an input though, not an output?  If it is an output, you may need a router.

If you are too far from your router to run Ethernet, consider a mesh system like this one:

If your DAC is pre 2010 it really won’t sound very good with anything but high resolution files.
What DAC are you using?
Would it be possible to run a long Ethernet cable to your audio room to see if that improves things?

A $25 repeater would be better than power line.
I've seen it recommended by reputable manufacturers.
No clue about a cable box. 

Anyone serious about Ethernet should check out Computer Audiostyle web site, there are quite a few threads on Ethernet,optical FMC to bring streaming up to cd quality.
It can be done with proper execution, attention to detail and imagination.

Mike, I,m using the DAC on my Mbl CD player.  My modem is about 30' away from my stereo, pretty far, IMO..  There could another option and that is I noticed an Ethernet port on the Verizon controller in my garage.  I would have to have it activated (presently it,s off) and I,m assuming its an output not input.  I could poke thru the wall and install an outlet fairly easily.  
Defintely looking into wifi mesh and wifi extenders.
I just bought this switch for my Fibre Optical setup.  ($199)

I have a OpticalRendu just sitting on my rack waiting for the Sonore Linear Power Supply and DC5 cable to be built and shipped. I also have a Sonore microRendu with their default switched mode power supply.  I am going to be using both with 2 DACs. I will compare both the Optical and micro on 1 DAC to see if my money was spent wisely.

That switch I listed above is seriously high quality. I do not hear a difference on RJ45 compared to my old TP-Link  (nor was I expecting a diff).  The Fibre Optical is the reason I bought this switch but even without using FIbre this is an incredibly well built switch.
NEW routers have faster wifi, 5G, if yours is old, ask for a new fast one, with wifi and 4 ethernet output jacks.

ethernet cable from cable co. router is without doubt the best for anything. I would poke thru the wall.

Is that cable company device in the garage wifi? Close enough for a good signal? You could try wifi from it before you poke thru the wall, 

You can buy a network switch, it will have 1 input for ethernet cable from cable company router, the switch will have wifi and 4 output jacks.

i.e. I put a wired switch near my home theater, then 4 separate ethernet cables to: TV; AVR; BluRay; PC and use it's wifi for strong signal in that area for tablet/laptop: reaches living room, porch, back yard.
“I could poke thru the wall and install an outlet fairly easily.”

That would be the most effective way to get ‘wired’ and noise free signal to your ultrarendu. I would steer clear of ‘audiophile’ network switch or hubs. The multiple LAN ports in these switches are prime source of noise. All of these network devices generate noise from the equipment itself along with noise from the AC adapter of the power supply.
Well, I just tried using a wifi repeater and noticed no improvement (or degradation) of sound quality.  Next step is a phone call to Verizon.  It probably wouldn't hurt to switch out the modem As it's almost 9 years old.  At the same time I,m going to talk to them about activating the Ethernet port on the controller.