Very interesting -- I can't compare the SST to the SST2, as I have never heard the SST. But I did compare the 4B ST to the 4B SST2. And the on the newer amp, the high end was more detailed and cleaner, the mids smoother, without sacrificing detail, and it definitely had more slam and grunt at the low end. And on tracks and volume levels that would make the ST clipping indicators flash red, I could not get the solid green of the SST2 indicators to even flicker orange at the same SPL.
-- Ian.