Sonos does allow upgrade discounts, once per item, you can see the details here: 

https://www.sonos.com/en-us/upgrade

I’ve never seen such a message before, though. Seems odd. Although I don’t have fiber, but the network that’s “slow” is inside the home, and the speed of one device really shouldn’t impact other devices….it’s just the speed of the connection between that device and the router. Are they trying to suggest everything should be 802.11a/c instead? It still wouldn’t, to my knowledge, impact other devices. 

Have you contacted your ISP for additional information?

Using some of the older WiFi standards forces your new gear to fall back to a slower mode to support these older devices, that impacts your new devices connection options and speeds.

I’d wire one or more Sonos to Ethernet and get them off your WiFi as my first option.

A second Access Point with a different clear channel (1, 6 or 11) and different SSID would be option 2. I think Sonos still is selling the Beam, it is a dedicated Sonos only AP, look in the Last-Chance sale section of the Sonos web store.

Hi @BeFunky 

Welcome to the Sonos Community!

All three of your Sonos products can connect to 5GHz, so I’m not sure why you’re seeing this.

I recommend you get in touch with our technical support team, who have tools at their disposal that will allow them to give you advice specific to your Sonos system and what it reports.

BeFunky,

I’m curious, which model FIOS gateway are you using?

I only just got FiOS last year, so it's the latest. I will look up the model number and post here.

We did have an outage last week (the whole) block. The performance seems to have improved -- at least no warmings at this time?

I'd need an A/V receiver to do that? My place isn't wired with ethernet.

Your gateway will usually have an Ethernet port.

An AVR would have no use in this connection.