It depends what you want to do, and where you're doing it. If you need closed phones due to external noise, then a great set of closed phones are the Sony MDR-V700. For a closed set of headphones the sound is quite transparent, and the bass is tight and well controlled. Great for DJing.. which is why you see so many DJs using them. If you want open phones, max quality, and you are using them alone in a quiet environment, I'd go for the Grado SR80.
I don't think anyone suggested Sennheiser HD25's. Which is weird, because for around that price there really is nothing better at all. Clean, clear and flat response with more handling power than the national grid!
I just bought a pair of Grado SR80(i)'s today. £95 new, from Richer Sounds. They advertise them at £110 but if you let them know you can buy them on Amazon for £100, RS will go down to £95.
Professional DJ headphones that suits your price range: http://www.com-shop.co.uk/index.php?main_page=product_info&cPath=7_133_224&products_id=12286 (Sure) http://www.com-shop.co.uk/index.php?main_page=product_info&cPath=7_133_224&products_id=226758 (Pioneer) http://com-shop.me
