A much better route is to treat noise at the source, Broadcom chipset vs Intel chipset in modem, disable wifi on router, emi-rfi contamination, power both via lps
Agree with @sns as a good first step prior to diving into FMCs and switches.
My advice is that switches upstream don't matter. Bad power supplies do.
Keep your networking power supplies (i.e. wall warts) off your clean power area. Use a separate conditioner if you need to, and consider using iFi power supplies for them if they are near your audio.
Also agree with @erik_squires as which tracks with SNS’ prior comment.
Personally, I was skeptical of FMCs until I had a positive experience with SGC FMC bundle to avoid compatibility issues when starting out. I’ve since progressed to a better FMC and more LPS throughout. Bringing it back full circle, I was surprised how much of an impact an LPS had on my generic switch, usage of iFi LAN iSilencer on other accessories, and separate power conditioner.
Nonetheless, I was just as skeptical as some in this thread, but experience can offer positive surprises for those that are willing to experiment - not always, but sometimes.