What to buy?

I just picked up a set of Sonos one speakers slightly used for 200 bucks! These things are awesome! I had previously bought a play three but returned it due to the inferior sound quality and reading several times how people had said that two of the One’s should out perform a single play 3, and they have thus far. I want an additional speaker to use throughout the home I now have one set up in my dining room and the other in my kitchen, but I’m looking for one that I can move around from place to place and even outside from time to time. My conundrum is should I pick up an additional Sonos One for $167 on Amazon (open box), or something else? I would like to be able to move one of the Speakers around the house and possibly outside as needed and I could easily do this with one of the speakers that I already have. This being said I could also save up and pick up a Play 5 later on or I could get the open box deal now and at some point later pick up a fourth speaker of some type? If I go with the third One I will have $367 in three smart speakers. If I wait and get a Play 5 I’d have upwards of $700 tied in. At that rate I could have 4 of the One’s for just a shade over $500. What I’m getting at is it better to have $500 in 4 One’s or $700 in two One’s and a Play 5? BTW I will only be listening to music and don’t need anything for T.V. Thanks folks!