I didn't really dig the Grado coloration, but loads of people swear by it and who am I to say they're wrong. Actually, I've heard that the Prestige Series gets brighter as you go up the ranks, but the Reference Series returns to the comparatively mellow territory of the SR60i, just with much more refinement. I wouldn't mind trying something from that series myself--there were things I liked a lot about my SR225i, but I never forgot I was wearing headphones because of that Grado signature.
Ironically for the OP, I ultimately went with the DT880, which I recommended against above. They're fine for rock (at least I think so), but it's probably not a strong suit. They have none of that Grado warmth in the midrange, and they're somewhat slower, subjectively. I still say go for the Grados, and if you don't like them, they won't be hard to shift. Unwanted Grado is an oxymoron around these parts.