These cans are not for the faint of heart.
Hifiman HE-5LE headphones are serious contenders for one of the best in the world.
The cheapest price I can find on these used is $614. Retail for these was $699.
For sale shipped CONUS for $500, Paypal preferred. Includes balanced and single-ended cables, extra felt pads and balanced-to single ended adapter..
For $50 more I will include the speaker tap for hooking up to the speaker outs of a regular receiver. Otherwise, you need a headpphone amp capable of at least 1 watt or higher.