Wired or wireless?
Do these need a wire to connect to a sound source? Despite being a bit of Senn fan (HD25 and HD26Pro are fantastic indestructible headphones) I have just sent back a pair of Sennheiser Momentum 3 wireless noise cancelling headphones because, although the sound quality, noise cancellation, and comfort, were great, the bluetooth performance was terrible - in an aeroplane where lots of other people were using wireless headphones, they kept cutting out horribly. I got a pair of sony wh1000-mx3 (such a romantic name) instead.