This is interesting. Where did you hear that they were close, performance-wise?
I've not yet heard the newest ICEedge modules, and may never have the chance as I don't plan on buying one. That said, I have owned amps with the ASC, ASP, and ASX modules. The ASC modules were used in Bel Canto's M-300 and S-300 amp, PS Audio's Trio A-100 and C-100 amp, and a host of other knock-offs. I lived happily with a Trio A-100 for more than a year. It had a very smooth sound which appealed to me. Here's a pic of the A-100 interior with the input board almost in view on the right:
I sold the A-100 when I bought a pair of mono amps with the big ASP modules which I sold within a month. Those amps had that "glare" I read about with class D amps. Next I bought a Bel Canto S-500 which had a pair of ASX modules. This amp had a squeaky clean sound which was appealing at first, but became boring after a couple months. From there I went back to class A/B and tube amps.
Of all those amps, the only one I could live with long term was the Trio series. Now, would stuffing module from Parts -express into a box sound the same as the PS Audio amp? I doubt it as PS Audio used a buffer on the input.
But I'm now enjoying a vintage Fisher KX-90 amp originally built in 1965, so what the hell do I know?