Headphone no cost limit.

STAX SR-009 with the right driver amp (usually tube or FET/Tube hybrid).

I use an old Stax SRM T1S driver amp, with NOS RCA clear top tubes.

STAX R&D uses a similar driver amp Today.

The driver amp makes a big difference, and only a few are real good.

Acceptable new driver amps are $2150 (STAX SRM 007TII) and up, to over $5000. Look at the Head-Fi website for more info.

SR-009’s are $4500 in the USA, and about $3500 direct from Japan.

Here’s a link to a site that covers headphones.

http://www.innerfidelity.com/frontpage

Click on the "Wall of Fame" link to see what the editor thinks of various headphones.

Best headphone?
Open or closed?
Dynamic, magnetic planar, or electrostatic?
Interface single-ended or balanced?
Power requirements, player type?

There’s a lot of variables to picking a headphone. It is also a growing hifi sector that has been bringing a lot of new technology to market.

Good luck in your search.

Best of them all , current in production.