Depending on how many ethernet drops you have in addition to the amps you will have in the rack, choose a switch with more ports than connections you already have for the main rack. You may want to look into Ubiquiti switches and access points. While any switch will be sufficient for Sonos products, (they only have 100Mbps ports and switches these days have at least gigabit ports) the Ubiquiti Unifi eco system has served me well and it is what I suggest.

https://store.ui.com/us/en?category=all-switching

 How far are the Sonos devices from the router?  Do they receive a strong enough connection if used wirelessly?

The router is on the ground floor but the speakers are on the ground, first and second floor. Yes, the signal should be strong enough. I have tested the speed on the top floor and it is more than 100 mbps.

 I’d try to leave them all wireless.  Check the SNR ( Signal to Noise Ratio ) on all your devices.  Settings ( gear icon ) - Pick a room under Your System - Pick a device under Products - Network.  Look for SNR.  Should be 45 or higher.

Hi @whyisthisallsoexpensive 

Welcome to the Sonos Community!

In short, yes - if you can get a cable from your router to the cabinet where you will keep the Amps, you just need a simple, unmanaged network switch to get all the Amps connected. I recommend a IGMP-capable switch that shouldn’t cost more than about £$€50.

If multiple Amps will be in one location, I do not recommend the use of WiFi - ethernet is a better option. In fact, I recommend that you disable WiFi on each Amp: Settings icon » iroom] » Amp » Disable WiFi.

An alternative would be to place an Amp in the same room as each pair of speakers - I would recommend WiFi for this setup, but you may need to move the wiring for the speakers (which may not be acceptable to you).

I hope this helps.