The hd580 floors me with the way they do good vocalists. I don't recall having that feeling with the dt250/80ohm, but I wasn't so focused on vocal music at the time I had them. Unfortunately I never got to audition the 250 ohm version.
I just decided to keep my hd600s instead of selling them because the extra soundstage width and the extra apparent detail is something i realize i miss every once in a while when listening to the dt250s exclusively. Still the dt250 does no wrong and I still stand by my statement that they are the best closed headphone i have ever heard.