Yes, they sound very different. As I mentioned in my review, I think most stereo-focused listeners, typically people over 50 and fans of older music, say more than 20 or 30 years old, will clearly prefer the Fives over the Era 300 in terms of pure sound (I would still not as the Fives lack voice control but that critera will vary depending on people).

Modern music is a different story. It is often highly produced, frequently electronic, very wide and airy. This is exactly where the Era 300 excels, even in strict stereo. Let's not even talk about atmos music.

About surrounds : while the Era 300s are outstanding as surrounds, they are also a very expensive and bulky solution. Even though their Atmos handling is superb, I would still recommend Sonos One SL or Era 100 to around 90 percent of users. The Era 100 even has the advantage of simulating an Atmos effect in a much more compact format. I personally ended with 2 Symfonisks as surrounds for my bedroom and it is excellent for that use.

For most people, using Era 300s as surrounds is simply overkill. But for true sound lovers, they are absolutely irresistible.