Yes, I agree. I'm a big fan of my HD580, and with the foam mod it's less dark too. I need to spend a little time with a 650 again though. The Beta22 should really improve what I heard the last time I had one.
I think the cost of the X-10 is about as high as I could justify, with as little time as I spend with a portable rig. I can't even consider adding a portable amp into the mix. Happily the X-10 doesn't seem to really need one.