Yes, the 580s can be great and sometimes more musical than the 600s. But you have to pair it with the right amp to get the most out of it (true for all phones generally).
Both can sound glorious, but how would I describe the differences? The 580s are warmer and maybe less resolving (even though they supposedly use the same drivers), but there's a suppleness and organic quality to the sound that is just hypnotic. But if you don't have just the right phone/amp combination, they can sound like a overly-warm, bloated mess.
The 600s, on the other hand, sound more dynamic and clear, but lack the suppleness and organic quality I just described above. They sound stiffer in comparison. Still, they can sound great.
For those of you who know tube amps, the 580 would be akin to a really involving single ended tube amp (like 2A3 or 300B), whereas the 600 are akin to a really good push-pull tube amp.
But, IMO, you have to get the right phone/amp synergy with both, it they can sound really wrong.
I will try both with the Vali when I have time and report back.