The Sony MDR-7506 are a popular choice in this price range for people that do audio for video. Not that any headphones are recommended as sole reference for mixing, but if you HAVE to use them, this one seems to be a de-facto standard. I use them a lot when I record, and I like the attenuation of ambient noise that they provide.
I assume you are talking about mixing music, though, and I don't know how well they work for that purpose.
- Martin