You find the 590 more laid back? I thought everyone said the 580/600 was more laid back. Is that what you meant?
Anyway, I've tried the 590, but only on a discman, and I haven't tried the 580 or the 600, so I guess my opinion should be taken with something pretty salty. However, I thought it was a good phone. The sound stage was better than any other headphone I've heard. (Mostly sonys with the F1 in the lead and a few other things hardly worth mentioning) It wasn't like listening to speakers, but it was certanly around me and not just in my head and that was nice. Even with the bad source it was fairly clear and had a reasonable amount of authority. I didn't find it to be too bright, but I seem to tolorate that more than most people even though I have good hearing. The detail was pretty decent too, but I think it would take an amp and a better source to bring it out more. People say they bennefit quite a lot from a well matched amp and a new cable and I belive it, it sounded for sure like they were holding something back. That said it would be pretty easy to find a lot of cans that didn't sound as good comming streight out of a discman. The frequency responce seemed realitavely flat, as advertised and I couldn't detect much color, though I doubt I'm qualified to do so anyway.