Sennheiser doesn't make closed headphones that I know about. Head-Fi, found at
www.head-fi.org, is probably the best source for headphone, headphone amp, and portable audio information on the internet. A good choice at the $200 mark for a closed headphone would be the Audio-Technica A900s, although they are very large (think CD-sized). I'd give you more suggestions, but I don't have much knowledge as far as closed or noise-cancelling headphones go.