Well... there is a LOT of headphones that will fall into that category, each having a simmilar quality of sound, with a slightly different tone answer the two following question as best you can if you don't mind please
what headphones have you had in the past, and what did you like about them?
What didn't you like?
I just listened to the HD600 recently. Here are my brief impressions of headphones I've listened to at various times.
Sennheiser CX300ii - Lively, brightish, loose bass. Hissy - probably needs a very clean source. Or did I have a fake?
Sennheiser PX200 - Clear, closed sounding but decent detail for an ultraportable. Warmish.
Sennheiser HD280 - Neutral, closed sounding, short transients (px200 was slightly better in this regard).
Sennheiser Momentum - Reasonably detailed, laidback (the cheap Philips SHL3300 sounded more alive to me). Balanced apart from being warm.
B&W P7 - Slightly more detail and spacious. Less balanced with the v shape but technically better than mass market headphones.
AKG K550 - Detailed, bright. Bass light, lacking body just outlines. Large earcups.
HD600 - Better timbre and detail out of the above, across the frequency range. Voices, saxophone and some other exotic instruments sounded more 3 dimensional. Better dynamics listening to the opening of Symphonie Fantastique. Balanced apart from being warm.
So the HD600 looks fairly good for timbre and dynamics. Reading old threads it seems the K501 beats it for clarity but is worse in other aspects. Some also suggest the HD600 could be faster more PRaT.