If you buy SR60 as your first phone, everything else will sound dull in comparison if that is all you have ever heard. If you are used to the Denon sound signature or even Sennheiser then Grado's will sound small and perhaps harsh.
For me Grado's are the ultimate for acoustic and Jazz, perfect for realistic timbres of unplugged instruments! I can see where the op is coming from in regards to rock music, electric guitar sounds gritty and textured but also fatiguing with Grado's IMO. But I also think the denons are a no go with rock too.. because of the reassessed mids. Senns are the way forward with rock, great mids and low fatigue.
I love my Grado's, can't imagine listenin to Coltrane without em!