When I saw your list, I wasn't that surprised. The HD580s are great headphones, but I don't hardly listen to them because they don't have the signature that I want for most of my music. I'm guessing that the price of the PP and the 600's have an effect on your ranking? In terms of "value" it's not surprising at all to see HD600's at the bottom of someone's list (not saying that's why they're at the bottom of yours). On the other hand, it isn't surprising to see them at the top of others' lists. Personally, if I spent the MSRP on HD600's, HE-400's, and X1's, I'd have a very hard time justifying the HD600 price tag.
Yup, you nailed exactly what I was thinking. I'm taking all aspects into consideration. I feel like I have more fun with the PP on my head vs the HD 600 and it doesn't hurt that I'm thinking, "Man, all this sound and fun for $40?!"