jisu: I haven't had a chance to compare - up to 2 months ago, my hi-fi setup consisted of my MP3 player and a 2-year old pair of HD280's. I bought the Zero while searching around for something to give my K701's more "oomph". I simply bought it because I was very impressed by the design philosophy versus the price (toroidal power supply, discrete boards, good quality soldering and cap placement). After 180 hours, it blew anything else I've heard out of the water in terms of raw driving ability, and after 300, got me to listen to music I would never have considered before (for example, I couldn't stand Gundam music before - now, I happily listen to it even without an amp).