It may well bridge the perceived gap you hear and will certainly do better than the KEF for low sound level listening since the Sub will allow the music to continue to sound rich by not being denuded of bass presence. Trueplay tuning is essential for best results where Sub is involved. 

However, all these matters are subjective preferences that will vary from one person to the next.

If you plan to go the KEF route with Sonos Amp, look for the non wireless version to save money on the unused wireless feature.

I have had the LS50W’s since they came out in 2016.  I prefer my stereo paired 5’s.  They are simpler and more reliable and can be used with rca, airplay, Sonos app or Roon. I’ve had reliability issues with the Kefs and their software is still bad although not as terrible as then they first came out.  I have a sub for my Sonos home theater with Arc and rear One’s but don’t feel the need for it with the 5’s.  You said you have heard the 5’s so am wondering in what environment because I have spent hours alternating between the Kef’s and 5’s and prefer the 5 sound quality.

I’ve had the Amp too and would not connect the Kef’s to it since they are powered speakers plus it sounds like overkill.

I have stereo pair play 5 gen 2 and a sub as my music system. And I have auditioned LS50W at my friends place. Overall I like the Sonos set up because:

1. Using both speakers with Spotify connect , they sounded similar to me because the source was 320kbps songs from Spotify. Perhaps with hi res music from tidal, kef May have an advantage?
2. Despite LS50 being an excellent speaker set, it’s still not full range 3-way. With play 5 pair and sub added I believe we have a full range set up. And with bass work transferred to the sub, the play 5s become free for handling highs and mids very well. I am a drummer and I especially appreciate clearly hearing the kick drum in rock songs and for that I love my Sonos set up. Adding a sub to kef would drive up costs and also invite hassles of matching / tuning cross over frequencies.
3. sonos software and hardware work smoothly. Although Spotify connect worked well with Sonos too.  However I am not sure if tidal has such ‘connect’ feature and you may have to use the kef app for tidal hi res (reviews of kef app are not good).

Note: for me, two play 5 give better stereo imaging when set up vertically with Sonos branding facing inward

if Sonos can bring hi res support then with the source sound improving it would really give the speakers to shine. And probably more value for money than LS50W at same price.

hope this helps

hope this helps

IMO, hi res is marketing hot air and availability won't make any difference to the conclusions here.

Source sound quality at the mastering stage IS important, but that has nothing to do with hi res.

If you have the right equipment it’s very easy to hear the difference.  Probably the only Sonos equipment it matters to is the Amp and the Five.  Good headphones and amp/dac are even easier to hear the difference.  I’ve taken the various tests like the NPR one and others and picked out the hi res four out of five teams and easily.

How did you make sure that this was a single variable test? For instance, variables like sound levels, mastering differences to name two key ones.

With sound levels remaining the same within 0.1 dB…

Unless the test is strictly single variable, how do you know which variable is driving the choice?

Oh please….

@SOCalistic 

You should be contacting the audiophile press.  For if your test was truly scientifically valid (double blind, volume matched, from the same masters), then you are the very first person in history to ever accomplish this feat.  

“Oh please” adhere to scientific rigor when making objective claims?  Why yes, please do. 

Digressing a little: the trouble with the scientific method, even for those that don't want to blindly drink the Hi Res Kool-Aid, is that it takes a major effort to pursue it at home in this instance.

And although I have no interest in the Hi Res offered by Sonos in S2 for music play, a spin off is that running a good test may have now become a lot easier - just downsample to 16/44 a Hi Res file that Sonos can play, and have someone play both versions of the same master in turn to you via Sonos without touching any volume control in the stream, double blind, and see if you can pick the difference in a statistically reliable manner. Because this way the other huge variable - of a different master being used - is also eliminated.

This, for those that are not part of the Hi Res marketing machine, even unwittingly.

This question has now been skewed by the release of the LS 50  wireless version 2. I find it very tempting as they added airplay 2 and seem to have fixed most of my issues. It would be great with Roon and Tidal MQA.  Pretty good chance I’ll get a set. 

A good friend bought a Meridian system which is worth about £25,000 in total. It does sound incredible, but he was also very keen for me to hear the difference Hi-Res makes. I tried my best but I honestly my ears could not hear any difference between the CD quality and Hi Res versions.

However by the time you’ve spent that much on your system, getting Hi-Res from Qobuz or Tidal is only a little more than CD quality and if it makes you happy, then why not.