Hi -- I'm amused by this lengthy discussion of 600 ohms v. 250 ohms models. I guess it would depend in part on your tastes and how you are using them, I think. I'm a classical musician primarily interested in classical and other acoustic music -- at least, that's the kind of music where I seriously care about sound quality. I've long found studio monitors to be the best choice for me. I want the utmost clarity, detail and neutrality, period. I don't want 'smooth', 'lush', or rich low bass, enjoyable as that can be for certain music. But studio monitors have often been heavy, uncomfortable and closed design where I prefer open.
I got the 250 ohm DT 880 Pro. Can't say I've listened to the 600 ohm model enough to say what the sound difference is. But I need the lower impedence so they can be used with a variety of equipment. A bit heavy, but comfortable, with breathable velour cushions and not those hot leather ones. And I can use them with my iPod Classic and Fiio E11. Ironically, the Fiio E11, though it is light and small and gives amazing performance for its low price, does have the smooth, lush bass I don't want, even with EQ set at zero. When I upgrade from the iPod to a portable that's compatible with FLAC files, I'll probably upgrade my portable amp, too.
But the DT 880 Pro has excellent clarity, detail and neutrality without excess bass.