It really depends on what you want out of the headphones. If you want headphones that are as accurate as they get in terms of frequency and phase response, the Beyerdynamic DT880s are your best bet. Their only real flaw is that if the mastering process was even slightly flawed, you'll be able to hear it. On the plus side, these have the flattest frequency and phase response under about $10,000. They don't have any significant resonances either, making them some of the easiest headphones to drive.
If you want some headphones that are more laid back, but still among the best studio reference headphones out there, take a look at the Sennheiser HD600s and HD650s.
You can pay a lot more for headphones, but if you want a flat frequency response, solid phase response, and relative immunity from the source, those are as good as you'll ever need.