Haven't heard the H2O as they are not distributed/supported in my country (the Nuforce are). But for whatever reason I hear more potential in the Nuforce design than the IcePower design (have owned and played with both. This view appears to me to be borne out by others, eg, Ric Schultz reports his modified Nuforce amps beat out his modified IcePower amps.
But there is no doubt H2O have had more time, and have spent much more refining the H2O than Nuforce has on their Ref 9.02s. I would strongly suspect that putting a large (and expensive) conventional power supply on and Ice module would probably make it sound better than a (inexpensive) SMPS supply on a Nu module. So I suspect the view the H2O is better than the Ref 9.02 may well be correct. I guess it depends on your point of view as to whether the comparison is apples/apples or apples/oranges.
But there is no doubt H2O have had more time, and have spent much more refining the H2O than Nuforce has on their Ref 9.02s. I would strongly suspect that putting a large (and expensive) conventional power supply on and Ice module would probably make it sound better than a (inexpensive) SMPS supply on a Nu module. So I suspect the view the H2O is better than the Ref 9.02 may well be correct. I guess it depends on your point of view as to whether the comparison is apples/apples or apples/oranges.