On a somewhat related note, I've never heard the Ref 6, I own the 40th Anniversary pre. I'm not sure if I'll ever switch, it's been an absolute pleasure.
However, I do own the new Ref 3 Phono preamp and it's an extraordinary improvement over the Ref 2. The dynamics are incredible. My perception is that I am hearing more information than I was able to glean from my albums in the past. Since the Ref Phono 3 and Ref 6 are fundamentally built on similar platforms, I am encouraged to believe that the positive reports on the Ref 6 are, indeed, true.
Happy listening!