What kind of sound are you looking for? A lot of this comes down to what your looking for. I own the M30s and while they have decent sound after about 40 hours of burn in, there nothing compared with my beyerdynamic dt250 headphones. They are a lot more comfortable than the Monitor 50s, and have much more detailed mids. They aren't bass cans that will rattle your head, but they also have a decent amount for typical use. Thats why it comes down to what your looking for. The price range you mentioned is really open. What I can tell you from personal experience is that while the M30s sound good and have many positive reviews they sound nothing like the beyerdynamic dt250s. Though if you do choose beyerdynamic dt250, make sure your buying an d80ohm version. I can power these with an iphone and they sound great. Nice rich bass, very clear mids....A lot of headphones that you will find under 50 will offer you a very v shapped sound. You will have your bass and trebles, but lack the mids. Or if they have treble (like the sennheiser 280 pros, they will sound tinny in comparison.
If your open to an open ear design, I cant speak highly enough on the sennheiser 558 and 598s. Both very similar sounding phones and extremly comfortable. But if closed is what your looking for I would spend a little more, make it the bang for your buck since this is a long term investment, and try them out. Give them a good 20 hours to burn in and they are sure to impress. There selling on ebay right now for 129.99.
If your looking to play it cheaper, while more V shaped sounding, the m30s are fun to listen to. But its all about what your specicifications are. You will definatly have more luck in the 100-150 range. The drivers are simply better sounding. If you can afford it I would recommend it. If not I would definatly take a look at the 518s if your open to an open headphone design. There more afforable and Ive compared them side by side with the HD 600s and they sound VERY similar.
Edited by stevenboe13 - 1/30/14 at 10:16pm