Headphones help

Hi. I'm looking for a new set of headphones. I'm fairly new to this, so cut me some slack if I sound stupid, okay?

Alright, so right now I have the V-MODA Crossfade LP. I like them, but I don't really like them that much for how much I spent on them ($80). I'm looking to find a replacement for those headphones. Here's my conditions:

• I prefer circum-aural/over-the-ear.
• I'd like the headphones to be noise-isolating, so that I can get rid of outside noise and focus on what I'm listening to. This is mainly because I'm a college student and I listen to lectures really often, but sometimes my roommates get a bit noisy.
• Since the V-MODA's were $80, I'm looking to spend no more than $50. I know this limits, but I don't want to go all out unless there are headphones that are REALLY worth it.
• I'll be using my laptop (Dell XPS 15z) 95% of the time. I probably WILL NOT use them for my mp3 player.
• Although listening and be able to hear my lectures is the main reason, I will also be listening to music and play some games from my laptop. So if the headphones can cover music and a bit of gaming, it would be a plus.

I think that's all. If I think of something else, I'll edit/add on to this. Or if you guys have questions, just let me know.

Thanks a bunch.

EDIT #1: I did some researching. I found out about Sony MDR XB500. They seem really good and fit my description. The only thing I can't seem to find out much about is how well they can separate outside noise from what I'm listening to.

Also, what about JVC HARX700? I couldn't find much on these either.