As to what made the different in my system, I can't say for sure. I did audition the H20 sigs TWICE, due to the generousity of Henry Ho. They sounded good. But the NuForce was more dynamic yet clean and unrestricted. When I put my tube amp back in after 3 weeks of the Ref 9.02s, the game was over. Had to sell.
Others have written about what I find so wonderful - the sense of ease. Although you can't tell at the time, by comparison, it was almost as if the other amp (ARC VT100MKII) compressed the vocals while the bands were playing (not loud enough to actually BE compression - peaks at 85db C weighted on 93db/w/m speakers (WP7s)). On the NuForce there seems to be simply more dynamic range on everything. I heard no bothersome artifacts - the tiny pop on turnon is tiny - hiss with no input I don't hear at all... the rfi isn't an issue in my system.
I experimented with various power schemes and 5? cords and various ICs and speaker wire. Tried both amps single ended and balanced.
Henry kindly sent the H2O back after I sold off my Transparent Ref cables - the H20 didn't like those network boxes! I tried Speltz back then, and later settled on Audience Au24, which is very very nice.
Neither the H20 or the NuForce was better on a PS Audio powerplant versus into the wall (dedicated circuit) no matter which Multiwave pattern I used - or even SIN. PS Audio HC Ultimate outlet didn't make a positive change on the amps either.
Once upon a time I auditioned several Preamps... the Ref 1 by ARC against the LS5MKIII. The difference I remember was what I'd say I heard between the H2O and the NuForce... with the Ref, when I turned it up, the music got louder. With the LS5MKIII, when I turned it up, I became more immersed in the music. It was more dynamic - more jump factor, I'd say. Same with the 9.02s.
Bob Wood