H2O amps were a bit of a boutique class D in the day for Apogees, especially Scintilla. Vince from Sacto (now deceased) was a rabid promotional fan. It seems the modules and topology were changed frequently with constant upgrade-itis, but that was several years ago.
I heard them on Vince's Scintillas, but he was badgering us to fall down in worship. I thought they sounded OK, but not necessarily revelatory.