I have first generation H2O Signature monos. They have been upgraded twice since, each time coming back more the winner. The thing about it's less powerful sibling, the H2O 100 is that this new model has benefited from all the upgrades administered to it's bigger brother. This is not to say the 100 still sounds better in some systems. I think the big H2O is way to powerful for most speakers. One thing is for sure, both amps can be vastly assisted through proper matching with wires and sources. Never has the adage, "What goes in comes out," been so correct.
I have heard the Butler in very good conditions. I don't know why, but the owner was way big into Tyco drums. From what I could tell, I was thoroughly impressed. I was still happy to come home to my own system.