Sonos play 1. Should I buy one or two

I've got 6 Sonos units and although not a fan of some recent app changes I've found the hardware to be excellent. We have them upstairs and downstairs with no dropouts or any connection issues at all.

W have a single Play:1 in the Kitchen and it does an excellent job.

I'm not sure what the SSID means or subnet. I have a router the ISP provided downstairs and a router I bought and hardwired upstairs (connect to the ISP router downstairs with CAT5). The WAP upstairs is strong enough to get all the speakers except a single "one" down in my office (the one that keeps dropping out). It worked fine for about a month, now it comes and goes so we just turned the Bose back on in the office with Bluetooth - it works flawlessly EVERYTIME. The Sonos is buggy and works some of the time. And, again, Sonos support is pretty crappy - so don't expect much after the sale, whether you buy 1 or 2 doesn't matter - you probably should buy zero and get something that will work (in my opinion).

I'm not sure what the SSID means or subnet. I have a router the ISP provided downstairs and a router I bought and hardwired upstairs (connect to the ISP router downstairs with CAT5). The WAP upstairs is strong enough to get all the speakers except a single "one" down in my office (the one that keeps dropping out). It worked fine for about a month, now it comes and goes so we just turned the Bose back on in the office with Bluetooth - it works flawlessly EVERYTIME. The Sonos is buggy and works some of the time. And, again, Sonos support is pretty crappy - so don't expect much after the sale, whether you buy 1 or 2 doesn't matter - you probably should buy zero and get something that will work (in my opinion).

This should be another topic, if it is not a troll.

But SSID is the name of your wifi network.
Your single speaker that drops out, are you sure it is connected to the upstair wifi. Since the upstair router is hardwired to the one from the isp router. The ip address is most likely 192.168.2.1. I would check if the single speaker that drops out is attach to 192.168.2.xxx or 192.168.1.xxx. If it is the second, you upstairs speaker is attaching to the downstairs router. Also check which channel you have the sonosnet on. Is it on CH1, CH6 or CH11. Most 2.4ghz routers operate from channel 1-10 as default, ch11 to ch13 are extended. I would suggest moving the sonosnet to channel11 vs using the wifi router default channel. It works better imho. If the problem presist, You might need to get a sonos boost to reach the back room. while wifi is good for 130ft, that is unbated distance. No walls in the way. Steel reinforced concrete is the worst, cuts wifi to about 20ft.