Is there a significant difference in sound from the 32, 250, or 600 Ohm versions? If I plugged each headphone into the same source, a dedicated amp and DAC, will one sound better than any of the others?
http://www.head-fi.org/t/513393/guide-sonic-differences-between-dt770-dt990-models-more
In short, the 600 Ohm variant will sound the best.
As an owner of 250Ohm DT770s, you will probably notice the difference more between 32 and 250 than 250 and 600. Cuz diminishing returns :P