You're very lucky to score a brand new pair at this time! Basically the same as the HD600, though the HD600 is supposed to have better matched drivers. Though most people will say the 580s and 600s are very much the same. You could buy the grilles from the HD650 and put them on your 580, I think...

Another happy HD580 owner here! I recently picked up a pair in great condition. I swapped out the grilles for HD650 grilles and it is one great looking headphone. It's a HUGE upgrade coming from my HD555's. Other headphones I've owned are HD280's and ATH-AD700's. The HD580's are my favorite of...

here's a picture of my HD280's opened up:

You kinda just pry them off with your fingers - try to get some fingers under one side of the pad and just pull up until you see some plastic revealed. Then try to slide your fingers around the whole pad. The earpad should come off as an entire piece with some plastic on the bottom of them...

While taking apart my HD-280's for a mod, the driver got loose and I saw the front of it - across it was printed "HD 555 HD 595". I just bought a pair of HD 555's as well, and just did this mod (soundstage does seem to open up but I'm loosing some bass). Looking at the driver, it looks exactly...