The HD580 is ok for rock, but not the best in the price range. I'm betting the SR225 would trounce them. I know the SR200 certainly does. I'm sitting here right now rummaging through some of my CDs I haven't listened to in awhile. One rock CD (by Bad Astronaut) in particular I've never really got to sound good on my system. I was listening to it a lot back when I had the HD580 and HFI-650, and I'll be damned if it sounds 10 times as good now with my Grados. Too muddy, veiled and laid-back on the HD580, too harsh and sibilant on the HFI-650, I didn't like it much with either.
The recording's still not the greatest, but at least I can really enjoy it now. The SR200 has a much better presentation for rock (on stage rather than quite a few rows back), deep and controlled bass, pleasant and detailed highs (not bright at all), a midrange that can make you just melt, and all the punch and kick you need.
I'd like to hear the HD600 w/ Equinox or Cardas on a really good system to hear what their true potential is. Whenever I make it to a meet I suppose because I really don't feel like bringing myself to shell out a lot of cash for a headphone so similar to one I quite disliked. I'm not quite convinced that with the correct cable/amp/source/whatever a headphone will sound completely different.
Ultimately I suppose then, how much you're willing to spend. Is it the best? Maybe if you build your whole system around the headphone to make it sound it's best. For the price though, and on most systems, I think Grados represent a much better deal.