Amp for Acoustic Zen Crescendo 2 ?

Wig,

Not sure if there is a sound difference between 845 or 805 tubes?

I would say from from my experience from either owning or listening to both of these big transmitter tubes they are more alike having several sonic qualities than being dissimilar.With equal implementation of same level of quality output transformers and each individual circuit design supporting the proper electrical parameters for each tube.Also would need good strong pwr supply's in each type of amp.

I personally have always liked the 805's vs the 845's,
They sounded more balanced and didn't have the upper frequency livelyness that a 845 sometimes can have.I owned a pair of the Mastersound 845 mono's last year but I didn't keep them very long.

And Offcourse I haven't heard all the different amps that use these big tubes.
Maybe someone else will have more insight on this question.

Kenny.

Bill,
I recall the same type of enthusiastic "the future is here now " talk with Devialet one box solutions that would render all else inferior.  Sorry, when I heard this brand/products I was underwhelmed to be polite.  Lyngdorf may be a better sounding product,  similar type of hype and predictions.  I just listen. 
Charles 

Wig,
The 805 tube has a reputation for high quality sound but for whatever reason isn't used nearly as often as the 845 or the 211 for that matter. 
Charles