i owned the 5a for five years or so. A great speaker and certainly a hyper good value at the $9-12 K range you see them being sold at....
yes I have heard the 5a carbon as well and find it sublime.
I own 7 mk2 with the M7 amps as well.
the carbon fiber/ balsa drivers are so low in distortion they are something to be appreciated with time......listen for ten twelve hours at a stretch.....amazing fatigue free clear pure water like flow....I cannot describe it...
i am actually thinking of trading my Treo CT ( good as they are and they are good.better treble than my 5a ) for the birdseye maple 5a carbons Sunny has.....
you might hear some 5 a owners making a fuss about not being able to hear the difference....and yet singing Richards praises....
I am 200% sure he is right with the new drivers....