im not really that into ht but apart from sound, good power (which both come from auditioning) i would also look at video upscaling. when you audition the audio part of it, it basically must sound as real as possible. listen to the range in parts i.e. bass, mids and highs. first listen to the vocals as they're the mids. then separately listen for the highs and lows. sound separation must be good as well - you can clearly hear each noise as a separate and not them meshing into each other. i had read once a person describing a movie in which he said that there was a machine gun firing and he could hear the sound of each bullet coming out instead of it being one constant noise. apart from that most of the amps that you would be looking at would have similar features in terms of software - dts, digital dolby etc etc