Why do I need a switch?

Perhaps.  Before I added the ethernet cables and running just wifi, a speed test on my TV would show >250mps.  I consider that a pretty good wifi signal.  Keep in mind that the main router is connected directly to the modem.  I am using a wifi 6e mesh system with the secondary router close enough to have a full strength signal.  

I ran the ethernet cable to the secondary router out of the audio grade network switch.  95% of the picture improvement was via wifi from the secondary router to the TV after adding the ethernet cable from the network switch.  The additional small improvement came by connecting an ethernet cable directly to the TV from the network switch.

After connecting the secondary router to the network switch, wifi speeds increased to 550 mps in the room with the TV.  

So I received and installed these,

TP-Link Gigabit SFP to RJ45 Fiber Media Converter, Fiber to Ethernet Converter 10/100/1000Mbps RJ45 Port to 1000Base-SX Multi-Mode Fiber (MC200CM) Black https://a.co/d/7JUU7Su

Easy peasy everything works and sounds good. There was no immediate difference and  It’s way to early decide anything, but without buying another $500 power supply, is there any decent LPS’s that have two or more 9 volt output connections that I can use on these network boxes? @erik_squires @jjss49 @zlone @mitch2 and all.

I use a Netgear PL1200. Then I run to a netgear 5 port switch. It sounds great. You can get faster models of this type if you want.

https://www.amazon.com/NETGEAR-PowerLINE-Gigabit-Pass-Through-PLP1200-100PAS/dp/B00S6DBGIS/ref=asc_df_B00S6DBGIS?tag=bngsmtphsnus-20&linkCode=df0&hvadid=80814222102152&hvnetw=s&hvqmt=e&hvbmt=be&hvdev=m&hvlocint=&hvlocphy=&hvtargid=pla-4584413749440857&psc=1#

There are other brands too, but the Netgear network through AC wire has been solid, easy to setup with pressing two buttons. One at the router and then at the Streamer location or desired device. This is not Audiophile stuff, but let me tell you it would be worth the cost to see if it meets your needs. I am very picky, not a critic, I just love HI Fi accurate sound and excitement from music. It sounds very good. It comes back with no intervention after a power outage. It just works slick. I have had flawless sreaming for 2 years now. A use the netgear switch to go between my Innous Mini Mk III, and a bluesound 2i.

First, know I have fully gone to the Dark Side of internet switches.  I started with a Etherregen with a quality LPS, added a SOtM with a quality LPS switch then the English Electric with a quality LPS.  I clock the Etherregen and SOtM with a Mutec Ref10.  I have the ENO Ethernet filter and several SOtM cables with filters.

My experience is more is better. 

If you want to start slowly I would suggest the Eno Ethernet filter, you should hear an improvement and if not send it back and stop.  From there a quality switch will bring another level of betterness.  The switch is a sum of its parts but key parts are the clock and power supply.  An off the shelf switch is not going to have a decent clock so don’t try it and its power supply will be noisy.  An external LPS is going to lower noise and you should hear it.

There is a level of diminishing returns depending on the resolution and noise of your system.  I am all in with streaming.  I used to believe streaming (Qobuz) could never sound close to a CD or ripped CD.  Now I know otherwise.

@curiousjim It’s way to early decide anything, but without buying another $500 power supply, is there any decent LPS’s that have two or more 9 volt output connections that I can use on these network boxes?

I used one of these from Solupeak on the streamer end, though my FMC's are 5V:

https://www.amazon.com/Audiophile-Regulated-Converter-Raspberry-Solupeak/dp/B08HDGCP3V/ref=sr_1_6?keywords=SOLUPEAK&qid=1680293203&sr=8-6&ufe=app_do%3Aamzn1.fos.18ed3cb5-28d5-4975-8bc7-93deae8f9840

The price has gone up significantly since I bought mine in December, but still affordable. I can't say that adding the LPS was night and day, but overall the fiber has been a nice upgrade.