[aamefford]

For a portable headphone, do consider the Beyer DT1350. Sound signature seems appropriate for you, and they are very portable and isolate well. They are on ear rather than over ear, so comfort does suffer. They also lack a mic option. I used them successfully traded off with IEMs when flying. As to customs, there are options in a similar price range as the W4's. customs are a bit more comfortable than universals and tend to isolate a bit better. That said, I am not sure I would get customs again. They do have many advantages, but so do universals.