I asusme what they mean is that a 580 with better cables is better than a stock 600.
Maxvla , good choice. I've not heard the 580s my self, but no one dislikes them. I did like the 590s, and I thought the 570s (which were right next to them at the store) were a far (and muffled) cry from the sound quality of the 590. They were really dark and muffled and they had about 1/2 the sound stage and they were just bad next to the 590s. The only thing going for them is that they have the same comfort level, which is high.
And everyone says sorry about your wallet to new commers becuase n00bs come here not knowing much about heapdhones, find out there is a huge world right under their noses that they didn't know existed, and then they get sucked in and want to spend a lot more money than they had originaly planned to. I came here with a $250 budget, did the same as above, and am still waiting and saving to meet my new budget.. I think my wait is comming to an end though. I just need to make a push and pick out some stuff for my self.
Well, have fun with your new cans, and welcome to head-fi.