I have an old PX100 (maybe not what you want to hear for this topic). Amped, it sounds pretty good, with tons of bass, and unamped it's nice as well. In absolute sound quality, it is not all that great (it's quite muddy, has huge bass which many might say can overpower the music, etc.) but its darkness, smoothness, fun colouration, comfort, and big bass (which I think actually sounds somehow "apart" from the rest of the music and thus doesn't overpower it) make it my favourite portable headphone, even if it was the very first one I've ever bought. It's simply relaxing and fun to listen to, and very coherent.