I was also looking/listening for something for the plane. Final E4000 (I did not get to hear 5000) seem to like more power than many of the cellphones would provide. They were not that loud even through a dedicated music player. You may need an amplifier with them which than makes it a bit less convenient for travel. Sound isolation is ok, but not fantastic. It will, of course, depend on your ear anatomy etc. Otherwise, they are fine piece of equipment.
SONY MDR-EX800ST sound fine, are not too expensive, do block a decent amount of outside noise, but may not be for travel. They are comfortable but protrude out of your ears just enough that you cannot lay on the side without them bothering you. Once you are on your back, they are fine.
The best improvement in sound via earphones that I noticed while travelling was trying to pick Boeing 787 whenever possible. They are somehow quieter. I do not know any measurements, just my small-sample impression. The rumor is that A-380 is the same way.