I currently own a pair of the CAD-211M Anniversary Edition monoblocks. I think they are the best amps Cary has ever built. I have previously owned the CAD-572 Mk.II, the CAD-805C, and currently own the Rocket 88 and the CAD-300B-SE. The Rocket 88 uses the 6550/KT-88 you asked about so I feel qualified to answer your question. I have never heard a Cary amp that sounded better than the 211. The shear power and depth it has are hard to beat. If I had to compare the two amps (and I will) I would say that the Rocket 88 is like a lake and the 211s are like the ocean. You can swim in both but the ocean is much more powerful and deep. There have been some relability issues but they seem to have been fixed in the latest incarnation. If you buy a used set of the Anniversary Editions make sure to send them back to Cary to have the power switch modification done. BTW, I use the SuperTNT 845M metal plate and Sofia 300B tubes with these amps.
