I'm currently using the GR02 Bass Edition and listen to mainly heavy metal. I would say that they definitely make listening to metal fun. Despite the name, the bass does not overpower. Guitars sound meaty, solos OK.
Another good thing going for it is little to no sibilance. I get annoyed by it easily. That's the reason I abandoned the SP51s. The GR02 doesn't suffer this problem, so solos, cymbals and high shrieks don't hurt the ears