Muslover --
I might be fairly well qualified to answer your question as I too, own an Audio Aero Capitole 24/192, and I auditioned the H2o stereo amp.
Bottom line -- I was not overly impressed. While the bass was some of (if not THE) best I have ever had in my system, the sound was just "lifeless". It was eminently clean and detailed, but again, lacked dynamic contrasts and full harmonic structure.
As I have read and heard nothing but positives about the H2o's, I and also Henry @ H2o, came to the conclusion that their was some type of impedence mismatch, or some other "lack of component synergy" between th Capitole and the H2o.
My advice -- I wouldn't even audition the amp/s unless you could borrow a decent preamp.
Good luck!