Pass Labs Amp X350.5 or X350.8 anyone compare?

I have searched for some opinions as to the sound quality comparison between the older Pass Labs X350.5 which I own and the newer X350.8.
It looks like the .8 does not operate as much in class A as the .5. But, that doesn't tell the story.
Anyone have a chance to listen to the newer X350.8? And if possible how does it compare to the X350.5?