Good closed-back headphones?

[Caliente]

Surprised no one has mentioned the Sundara (closed) - an easy drive, though not the same sound signature as the open version

 

[Drumhead]

Neumann

 

[Gethyn]

Any of the Sennheiser HD models would fit your budget (especially if going used). The Philips X2 and X3 are excellent in my view and often overlooked.