I haven't found one but, I'm sure you know about:

http://www6.head-fi.org/forums/index.php

http://www.sgheadphones.net/

http://www.audiocircle.com/circles/index.php?board=74.0

http://www.wireddaddy.com/

(Although Wired Daddy doesn't have that much content yet)

http://www.headphone.com/

Also, 6moons frequently tackles the subject and of course I always dig Stereophile's own Mr. Phillips.