Interesting situation! Do we need this....

I’m with @carlsbad. We have to note that despite their embrace by so-called audiophiles, there are a LOT of USED KEF LS-50 and now LS-50 Metas for sale relatively cheap on eBay and other outlets. That alone says that maybe they grow old fast on people. I mean for a small little thing on a desktop maybe, but I’ve never understood the draw of such baby speakers in a decent sized room unless you add a good subwoofer to them. To each their own. If you were happy with the sound from the Fluance then be happy. Sometimes the brain and psychoacoutics can play tricks on even the best person calling themselves an audiophile. Many people upon hearing a X priced whatever will think, "Oh man that does sound good" until you tell them it was not X priced but Y priced and much cheaper.

Don’t get me wrong. Nothing bad about BETTER quality gear that is often pricier, but measurements aside, "better" is in the ear of the beholder.

There's also this thing called "synergy" where it is the complete system that delivers the goods that matters.  Perhaps your amp was happier driving the Fluance than the KEF.

@moonwatcher the used prices on Ebay seem in line with most used speakers. One of the reasons for a lot of used units is likely that a lot were sold. Even my local discount retailer has them on the shelf. I doubt there is a more popular non amplified speaker. Unlike most speakers, they are easy to ship hence more conducive to Ebay/used.

@thespeakerdude perhaps, but if they are soooo good, then you’d think people would be keeping them for use in a secondary system, or passing them down to relatives or friends, not pawning them off on eBay. Most speakers I have bought have been repurposed or given to relatives to get them started in this hobby and especially move up from cheap soundbars. I don’t know, maybe people buy them based on the hype, but then find out they just don’t fill a large room like they expected, and they live and learn and move on. This isn’t a knock against KEF or their good design. They image extremely well.

If there were more brick and mortar stores around where people could audition speakers before buying, there wouldn’t be as many for sale on eBay. But those days are almost gone. If they could, they might get the R3 instead and be happy for years and years. 

@anotherbob - I think the OP was simply sharing that when he thought he was listening to one setup it actually turned out to be another one that he wouldn’t have expected to be as good and it “lesser” combination compelled him to enjoy the music. 
 

It will be interesting to see what his experience is with the intended combination, but he never said that the “lower expectation” speaker was better. 
 

It kind of reminds me of the Bose demonstration where you think you’re hearing large speakers and then they reveal the little one. It’s fun when something sounds good enough to trick you into thinking it’s something that you’d expect to be better. 
 

Sometimes it’s expectation bias and sometimes is a high value product, but either way it’s nothing more than a compliment to the gear of the listener enjoyed it. 

All this may say something about the relative quality of the Fluance speakers and the drivers they use. I've never heard them...wasn't a fan of the yellow drivers just based on looks. Good luck with your project if you intend to finish it.