Some DACs and some amps can definitely cause harshness in a headphone that shouldn't been there. But I've come across headphones where sibilance and excess sparkle doesn't really bother my ears at all. I wouldn't call the HD 600 sibilant unless it's on a sibilant system. The HD 600 has amazing tuning. What I personally would call the HD 600 compared to higher-end headphones(such as the HD 800, various orthos, Stax, etc.) is a bit slow in its transients and a bit blurred and gritty(which can be fatiguing to some people) at times in comparison because of that.