Technically, the HD650 is probably a small upgrade from the HD580, but the biggest difference is obviously tonal. I would not blindly upgrade to an HD650 from the HD580 because they are just different variations of the same sound. If you love the HD580/600, but are looking for the same tonality with a more fleshed out and bigger sound and impact (and more bass), than you might want to consider "upgrading." I still recommend you listen to the HD650 before purchasing if you can, because you may be disappointed how similar the 650 is to the 580/600.