Here's Dick Olsher's review of the Crescendo in Absolute Sound.
10-01-14: Branislav
Acoustic Zen Crescendo...and laugh all the way to the bank :-)
Not only could he drive it with tubes, he got particularly good results with Triode Corporation M845SE SET monoblocks. According to his measurements and component matching, the Crescendos present a benign impedance curve for tube amps.