Randy, I own Audible Illusion and CJ PV-12. The AI is class A, while the PV-12 is class B. Both are tube, and both sound good; the short answer is size and quality of the "sound stage"; the AI is more definitive and has a larger sound stage. They are also on opposite ends of the sonic spectrum; one is neutral while the other has a certain "tube glow". Class A contains a very wide quality range, as well as price range; however, it's pointless to buy one expensive piece if you can not afford to buy all the expensive pieces in the chain, because a chain is no stronger than it's weakest link.
I've heard incredible top of the line ARC, especially in regard to definition, but it's too lean for my taste, almost like SS, and I prefer "Primaluna" which can come close to ARC with the right tubes. There are a number of different factors in regard to Class "A" sound, and now I'm speaking of the same components that have earned the Class "A" rating; that is why you have many decisions to make before you plunk down a large wad of cash; such as tube, or SS, and all the things you prefer in a pre-amp. I don't know how you go about making all those decisions, but they are necessary.
Enjoy the music.