The 250 ohm has been rated by most people as either identical in performance to the 600 ohm or slightly better-sounding. Some high-end users with expensive equipment who have A/B'd these phones have said the 250 ohm is much better.
I'd go with the 250-ohm because it uses a newer driver (the 600 ohm drivers are a holdover from 1985).
I own the DT770-250 and I have something to say about the DT770 and rock: They produce a more realistic image than the "neutral" DT250.
Here's why.
I have played electric guitar on numerous occasions (with earplugs!) and jammed with my electric violin for many hours with really talented rhythm guitarists. When a rhythm guitarists hits a hard chord and lets that chord decay while palm-muting, a massive low-frequency sound is produced by the guitar as the note decays. This sound is almost entirely absent from the DT250-80. It is reasonably present with the DT770, almost "live" sounding.
There's just too much midrange for my tastes on all of the headphones I have tried but the DT770.
I am a concert and solo violinist, and also play much rock and fusion music on the side. The most realistic musical impression of all headphones I have heard comes from the DT770.
The treble is also quite clear, making distorted guitars more apparent. Might be fatiguing for some but seems very transparent to me. If you're looking for a natural reproduction of sound, you've got a good headphone in mind.
I listen through a 4.5v airhead and sony DVP-NS500V.
For your kind of music, the DT770 will perform very well. Harsh treble on bad recordings will really stand out though
Cheers,
Geek
Edit: By comparing the DT770 to the DT250, I am assuming the DT250 sounds relatively similar to the Sennheiser HD580; at least, that's what headroom stated- the closed headphone most closely resembling the sound of the HD580/600 is the DT250. I have not heard the HD580 yet. However, I think the DT770 will work for you better than the HD580, but keep my personal bias in mind when making your decision.