I'd vote "you want a set of RS1", too -- and ideally a great amp that is versatile enough to drive different phones, but with the RS1 you get a lot of slack with the heaphones mattering a lot more than the amp (need I qualify all the usual "IMO" etc?). If you have or want to get a used Marantz or NAD integrated amp with a heaphone jack, that'll go a long way toward showing what the RS1s can do. Better amplification if you are committed to optimizing once you figure out how much you like them.
I also think "Grado for rock" talk is overblown in that the RS1s are highly resolving and highly "musical" on whatever-genre. Perhaps if you're all about soundstage/headstage, then they''ll fall down in comparison with others. And perhaps they're particularly uncomfortable for you (I will say Sennheiser makes some amazingly comfortable headphones!). But the RS1s are great across a bunch of genres. Classical chamber music (string quartets, classical guitar, piano trios) are great. The Hank Jones/Dave Holland/Billy Higgins trio record "The Oracle" sounds amazing on RS1s. Decidedly not "rock". Bill Frisell's quintet records sound amazing (electric guitar, and a range of other instruments, not rock. Maybe the "rock-mainly" Grado admirers would give me this one, given the electric guitar and its variety of tones).
That said, try the Sennheiser HD800s just to see if you agree that they fill in a gap (i.e., if you don't think classical or jazz sound good on the RS1s), or the AKGs or whatever else you might want to try. The amp matters more, here. And you might just dislike the Grados like some post-ers here do. In the long run though, that just means anyone's advice is useless in comparison to you checking out with your own ears a few different things.
