I'm listening to the Denons right now, I got them last week, and they've been very, very enjoyable. Very clean sound, clear, with a present bass, and great mids and highs. It's great for it's price. Search around the forums for the couple threads on them. I can say they're a great improvement over my XB500s, and I think they sound better, including the bass clarity, and not slightly overextended like the 500s. The Q40s are also a nice choice, and go on sale occasionally. Keep taking other's suggestions though, I'm not very experienced, especially in any high end gear. Take other's words higher than mine.
A warning on the HP700s though, they take a bit of breaking in to feel comfortable, for me at least. A couple days of discomfort, but by now my ears have adjusted and they're fairly comfortable for DJ phones. Here are velour pads you can buy that fit: http://www.zomo.de/en/Products/Headphones/Zomo-Headphones-Earpad-Set-Velour-S-for-Zomo-HD-1200.html (more colours: http://www.zomo.de/en/Products/Headphones/Earpad-Set-Velour-for-Sennheiser-headphone-HD-25.html )