I would seriously consider a pair of in-ear isolating earphones instead, such as those made by Etymotic Research. They do a far better job of blocking out noise you don't want to hear than phones that use active noise cancelling technology. I have a pair of ER-6i (which you can get from Amazon for around $80) that I absolutely love. Not only do they do a great job of blocking our sound (whether you're listening to music or not), but they are some of the better and more uncolored headphones I've had the pleasure of using.

Since your budget is $200, I'd consider the ER-4P.