I know that the models offered by Audio Technica and Grados score highly with music lovers who want a high quality sound from a well-designed set of headphones; these are choices I pretty well agree with; Sennheiser are also pretty good, and I have had them in the past.
However, for that combination of audio quality, build quality, portability, and sheer style, (the criteria set out by the OP in the original post), to my - perhaps prejudiced, and certainly jaundiced - mind on such matters, nothing touches the Bowers & Wilkins P5 headphones. They are superb, portable, very comfortable, look great and sound terrific. They are easily the best headphones I have ever had; I also have the B&W P3's - which are even more portable, very stylish, and offer exceptionally good sound as well.