1. What was the listening room like? It it was a dedicated room, then that validates an impression. If it was a regular speaker setup on a storeroom floor, then there's reason to wonder.
2. Were you standing or sitting? A lot of people who are in stores evaluating equipment remain standing. That means that the top reaches their ears, but does not get balanced out by the mid drivers, which are pointed at their chest or abdomen.
3. You say you didn't like the music you were listening to. Did you try music you knew? It could be that the music you evaluated was harsh in the top -- I trust you listened to a range of tracks before forming your opinion?
4. DId you check the settings on the amplifier? Were they in neutral?
5. Silly question: Were you in the sweet-spot? I find that the definition of mid and top changes quite a lot, with any speaker setup, if my head is one foot in front or behind a given listening position ...
6. You might want to include a description of the other components in the signal chain when delivering this kind of verdict!
7. If all of the above were controlled for, now we can begin evaluating the use of the ICEpower modules.
As Alex mentions, you have to implement them correctly. But one would assume that Bel Canto has done that, and that the signal out from their component should be fairly agnostic as to what it is connected to.
Still, speakers do have their signatures -- and if a particular speaker is configured to deliver in the top, then ICEpowers ability to deliver definition in that region may give too much icing.
I'm not out to defend ICEpower. If you listen to something, and don't like it, then you shouldn't buy it - whether it's tube or class-D. Peoples' hearing differs to an extreme amount, and actually makes it very unlikely that one person's experiences are valid for another (seriously.)
In the BeoLab 5s the technology has been implemented quite successfully, but I have also heard solutions from other makes, in direct comparison to other technologies, that have been very, very good.
To finish: which Stereophile article are you referring to, considering ICEpower and its delivery in the upper frequencies?