The Superlux HMD 660 is an headset version of the HD600 reviewed here: HD660 review
The main difference is the use of a different cord/cable. I find this one better than the original cord of the HD660. It is a little longer and less rigid.
The mic is a dynamic one mounted on left side on a flexible mount. It is perfect for computer application (skype, teamspeak etc…) but require a 12db mic boost on my integrated soundcard. It doesnt work well with professional preamps (EMU1616) so the target is clearly for use with a normal computer card (gaming application, communication)
The sound signature is similar to the HD660. It makes this headphone a good all rounder for computer use (music, films, games). The closed aspect can be usefull in a noisy environment.
For the price it is a good competitor with traditionnal computer brands but it doesnt include a soundcard witch is not a big issue (it works well with integrated soundcards)