Bowers & Wilkins P5 over-ear headphones:
http://www.bowers-wilkins.co.uk/Headphones/Headphones/P5
They're essentially the mobile equivalent of the B&W MM-1 speakers I use with my Mac. In my opinion, it's an unbeatable combination that complements Apple products like no other.
Seriously, though, the sound quality (and more importantly,
accuracy) of both is excellent and well worth the money. Beats, no matter what people might say, are all flash and little substance. They sound impressive, but are very poor in terms of 'high-fidelity' and cause a lot of listening fatigue. That's coming from experience of owning a pair of Beats Studios, by the way. Also, the P5 build-quality and design is unmatched (again, in my opinion).
Oh, and the P5 iPhone remote/mic is awesome.