Excerpt: it may be worth paying the $ extra for the HD-650s for the better cable. But the 600s sound excellent and are very comfortable. You might be able to get the same sonic quality for less but not with the nice ear pads I suspect.
Summary: These are very good headphones for the money, quite balanced sounding. Yes there are some headphones which can do this and that better technically, but somehow not as balanced overall and not as natural in the midrange.
Summary: I am going against the grain I guess. These cans are good, but they don't live up to the hype. The first time I demoed these they were going through a Creek headphone amp and after 20 minutes my ears were ringing. I told the salesman and he thought I was on glue.
Excerpt: I bought these headphones as an upgrade from my Sennheiser HD570, and the sound is much better. They are plugged directly into the audio out of my computer, for music/movies/gaming. I was afraid the high impedance of the HD600 would demand a headphone amplifier, but they work ok without one.
Summary: The HD600s were my main phones for a few months. I could listen to them for longer than any other phones because of their relaxed presentation and wonderful comfort. They were satisfying phones for classical music until I upgraded to the HE60.
Summary: Construction-wise, the HD-600 is a little delicate. No, the HD-600 is not poorly constructed. Rather the headphone is designed for home use and is meant to be light and comfortable (and comfortable it is). Just don't plan on bringing it on too many bumpy trips.
Summary: For many years, the Sennheiser HD600 is one of the best dynamic headphones on the market. But though it has been supplanted by the HD650, the HD600 still holds its own. The bass is liquid, as are the mids and the highs - very well balanced, though the bass could be a tad less lumpy.
Summary: The HD600 are very good headphones, but presently the same basic sound signature, but better can be had in the HD650, and the same exact sound 99.9% can be had for less money with the HD580. As such I don't see the value of the HD600 at this point in time.