Sennheiser HD-580 or 600. I don't know if that's too big for your purpose, but upper end Senns sound heavenly for me, with the right source and headphone amp.
Best portable headphones and DAC
The operative word is PORTABLE. I like my current set-up (which consists of an AQ red dragonfly and a folding pair of sennheiser headphones.) but I,m wondering if there is anything better out there. I also have a chord mojo but I,m not sure I would categorize that as portable. It mAy be fine for taking on a flights but it's too heavy for walks or bringing to a health club , IMO. I'm debating about upgrading the dragonfly to "cobalt". The reviews are mixed as to whether it's worth it if you already own the "red".