Thank you so much for your very comprehensive reply. I very much appreciate it.
I'm stuck with the Sonos system for a while as its impractical for me to have anything else - at this time. (more KFC Mum?)
However, I will certainly upgrade to a `proper' system and am indulging my nerdy chromosomes in research, so I'll be prepared for that day. I have an old SACD of David Bowie's Heathen with a 5.1 mix.
I played it the other day and was shocked at how awful it was. When I purchased it nearly 20 years ago, I had a Sony Home Theatre in a Box system, and I thought it was terrific. Over my Sonos sound bar with the two rears - yuck! DB's voice was crystal clear front and centre, but the band sounded like it was half a kilometre away. Lol.
Playing the stereo version of the disc was still lovely, though. The two-channel stereo over the Sonos system has a pleasant way of surrounding me with music. I can still listen to Atmos from Tidal and Apple, and I like it. However, this has switched me onto the possibilities of a good, audiophile-level surround sound system.
Thank you again for your help.