The new ProAcs are very good and retain the warm, smooth and natural sound of older models. They are very good at integrating the ribbon tweeter with the other drivers, something that cannot be said of most speakers employing ribbon tweeters. I don’t know about durability, but, it should not be hard to replace a tweeter if it did blow. These days, that kind of failure is not that common unless the speakers are pushed really hard.
Thinking of upgrading speakers from ProAc 3.8 I have enjoyed in my system for 23 years.
I am likely to buy slightly used. I have read the newer ProAcs have tighter base and are easier to place in your room due to down facing port. Are the ribbon tweeters that much better? I am concerned about durability of the ribbons, as there have been a few threads by people who have had ribbon failure. I would consider D48R or K6 if I can find a nice used pair. Do the newer ProAcs lose any of the magic of the older models? Another speaker that interests me is the Sonus Faber SarafinoG2.
System is Accuphase E406, Nottingham Spacedeck, Allnic H5500