I like the idea of second hand REF 1's...even if it takes more time to save. You already know you like KEF & the REF 1's are phenomenal. I saw a pair for $4500 on my local Marketplace not too long ago. Those Monitor Audio's look legit. I have eyeballed them as well. But my limited experience with ribbons & AMT tweeters has not been fruitful long term.
I ran the R3 Meta's in my living room for a little while but eventually sold them. Nothing was wrong with their performance & I liked the gloss black look but I replaced them with a pair of Fritz REV7 SE bookshelves. Glorious midrange & vocals. Fritz has a few different models of speakers & you can request one type of tweeter or woofer over another if you have personal preferences in such things. Home trials as well.