I bought one last October on-line in which it sounds great but somewhat uncomfortable for my big head. Strongly recommend you try-one-out on your head before purchasing.
I agree with tibas92013. They are a bit uncomfortable and fall short in the comfort scale amongst the headphone arena. I do a lot of video editing for work and occasionally some audio mastering so I've had no choice over the past decade to dive deep into the headphone world.
I own the M50x's as one of the many in my collection and although they are good, they are not great if you're looking for something that produces a balanced sound presentation. Would you mind sharing with us what you're looking for in a headphone? This is by no means to talk you out of anything, I'm just making sure we can provide you with options in case you are open.
Most people like the bass, treble and then mid's in headphones, which is typical. The M50x's will give you mid's, bass and treble in this order...to keep it simple.
If you don't care about having, "the pounding bass in your head" feeling, and want something that's well balanced and comfortable, I'd also look into the Sennheiser line, starting from the HD558 and up. They are excellent in their sound presentation and very well balanced.
I'd also highly recommend getting an amp/dac to pair it with your headphones. You can get something simple as the FiiO E6 for about ~$30 to the E17K which is ~$130 range. You'll experience a whole new world of sound and won't be able to go back.
However....if you're just wanting something that's plug in and play (considering that you're looking into the M50x's and that price range) I'd also recommend the new Bose QC 25's. They are from my experience the best noise cancelling cans that produce a well balance sound presentation, that are also extremely comfortable, light and classy.
There is an excellent online community forum that you can also check out. Just google "head fi," and it'll be the first link that pops up.
Hope this helps...let us know if we can help further...
Cheers