How does the sound quality compare between the PX 450s and the ATH-M50s? I haven't been able to find a direct comparison. Which has better sound? And if one is better, by how much?

Thanks for all the helpful input. I really want to get a full set for my first pair of nice headphones, but I'll probably get some earbuds pretty soon down the road. Right now I'm thinking about the M50s, maybe the Sennheisers. I really appreciate all the help.

I'm brand new to the world of high-end headphones, but I love music and want to take my listening experience to the next level.   Let me set out my parameters. I'm a college student who's going to be wearing these a lot while studying, so a few things are very important to me. One is...