I'd like to keep the budget to a $500 maximum but honestly it doesn't really matter to me.
Portability is always nice, but I rarely take my headphones outside of my room anyways so it's not that important either.
As far as amplifiers go, it's not really something I'm looking to buy at the moment, but If you could recommend some good models/companies, it would help out in the future.
But if you know of a significantly better pair of headphones out there that isn't too much more expensive than the three I have listed, I'd be interested in hearing.
Note that a solid bass is one of the most important things I'm looking for.