For now I would recommend pausing any plans to buy Sonos products. They make great speakers for sure but since may Sonos released a whole new system for the app which was very premature & it’s impossible to use. There’s so many bugs & very unstable you. And it’s not about extra features but you literally can’t play music anymore, the playlists aren’t working you can’t connect to your speakers and these kind of stuff that are vital. 

I have a Play:5 and it sounds good on its own but I don’t use it in a context where the stereo image matters to me. I would expect two of the new Fives to sound really good and offer full range stereo.

I also own a pair of Era 100s that I use as surrounds with an original beam and a Sub Mini. I think that the Era 100s sound great and might do what you need without the Sub Mini. That said the Sub Mini definitely adds feel to the bottom end. 

I would suggest that you take note of the issues people are having setting up new speakers with the new app and maybe wait a month before making a purchase to allow Sonos to fic the app issues. 

Thanks for your advice Graham & Nieszka, much appreciated. 
Graham, I have always use a sub woofer with various set ups, but what I’m wondering is would I get a better sound with a 2 x Five’s, than I would with with 2 Era 100’s + a sub mini? ie. are the woofers in the Five’s as good a using a stand alone Sub?
Tough question I know…..I appreciate it’s just an opinion.
 

I wouldn’t get 5s so late in their product cycle. 

Because a newer version is on its way? I thought the Fives were the replacement for the Play 5 no? 
Do you have a view on the question above?

It is a hard question and a lot depends on the room you will be installing the speakers in.

What I can say is that the Era 100 has really impressed me. The sound is fuller and has more depth than I expected.

I would probably be replacing my 3 Play:1s if the issues with the app had not interrupted my enjoyment of music played on Sonos.

Basically the same as the old speaker. its way behind the Era 300 in terms of memory, rom size. No idea if it will be replaced. 
 

For me it’s too much a past generation speaker to buy at full price. Steep discount maybe. Just my opinion. 
 

I can’t comment on the era + sub mini vs 5 as I haven’t heard the era combo. But the old play1+sub sounded pretty damn good. Sound wise both options will be very good.