I've used 4 Icepower amps (all from PS Audio), two of which were modded by Rick Cullen of W4S. I still use the modded C-100 integrated in my office and as a backup to my Hypex NCore NC-400 in my main system. I use RAAL tweeters in my office speakers, and have done so in the past in my main system too.
Before I got my N-Core, I was happy with a modded GCC-500, but in comparison to the N-Core the top end is somewhat soft and diffuse sounding, and a bit veiled overall. Not "bad" sounding, just different. I don't doubt that it measures flat, but top end events do not sound as clearly and sharply defined, which makes it sound like there is less top end energy. I suspect it is a psychoacoustic effect, not an actual rolloff. My modded C100 sounds much the same. The RAAL tweeter still sounds great with the ICE (better than most other tweeters, IMO), but as a high-rez device it will display changes and improvements in the signal chain very clearly.
Are the newer ICEPower modules better? I don't know. For the $, they still offer a lot of performance (very nice bass, clean, quiet and smooth), take little power, run cool, etc. Good Class AB amps can sound more lively, but not necessarily better. All amps will bring their own signature to the party, and comparable quality AB amps will cost more than the ICEPower amps in general. Odyssey makes great amps for the price, which I think are AB. They might be worth a look, but don't discount the W4S amps. They bring a lot of quality for the $.
You could ask W4S what they think of the sound of the newer modules, vs. the old.
Good luck.
