Well when Ikesound decides to fix my QAA4250 dilemma, I'll be running it to push my front stage. 250x4 ftw!
As far as sound quality, there are no sonic distinctions between amps. One amp isn't going to be "warm" sounding just because of X and Y components. But out of the box, there IS a different, most likely because of different frequency response. Not all amps have the same FR. An amp that has a bump in the 700hz region and it'll sound "warm." If you hear a difference, it's because of FR, not because of the pixie dust. Even Richard Clark made a point that not all amps are the same unless you isolate all variables except for the amplification itself. After that, no difference.