copy of my post from HE-4 thread - I think you might be interested:
"I have just powered up my new emotiva a-100 and HE-4, oh boy what an amp, first notes and I already know it is mighty as hell, very refined and so effortless, no hiss under any conditions (when there is no music and there is quiet in my room very slight hiss starts at about 1 o'clock but that's with my ultra sensitive hearing for any noise/hiss/buzzing etc so this is really great - I will never go for that volume + when there is music playing it would be undetectable anyway), volume range when using 2,5V rms level output from dac is at about 8-10 o'clock but the power can be felt immediately - the same impression like listening to the LYR, it is less bright than EF-5 which is very good for HE-4, very neutral
no sign of distortion because of running out of power, compression effect or clipping with high dynamics peak, 8-10 o'clock is like on Lyr's full power, so this is a freaking little monster amp
it is actually better to switch to 1.25V rms (usable range is then from 9-12 o'clock so I can skip some slight channel imbalance at the beginning of the pot about 7-8 o'clock and have wider volume range)
damn this amp might be nice with HE-6 indeed pumping some power and should be amazing combo with HE-500"