An excellent sounding headphone for the price. The 650 is what separates a mid-fi headphone and a hi-fi headphone. It is has extremely rich bass and excellent mids. The headphone does require a little amplification, but it is not too difficult to drive. The headphone is extremely comfortable- when broken in. when you first get the headphone, it clamps a little hard and the earpads aren't very soft, but both loosen over time. Some people may not like the "dark" or more warm sound, in which case they go for the hd 600, but if you do like the warm but not overly warm sound this is a extremely good headphone. It sounds excellent for classical/jazz, acoustic, rock, and metal. The bass is creamy yet slightly punchy, the highs aren't piercing but aren't laid back. The soundstage and natural reverb the headphone adds is sublime. Once the headphone pads wear in the comfort is unrivalled.