I took a look at the Razer Naga on that site, and I'm wondering how all those buttons on the side works. Can I bind actions to them like hotkeys on my keyboard?
Yes, that's what they're for. It's an MMO mouse. You can effectively bypass the need for a keyboard (except for chat purposes) in WoW (not that I would recommend doing so).
You should go to Best Buy and hold some of the mice. They have several gaming mice, including Razer and Logitech. Also, you can buy them, and if you don't like it, return it. Or you can try it, and if you do like it, return it and buy it online for a much cheaper price.
If you're super picky like me, it might take some trial and error before you settle on one. If you are someone who doesn't lift their mouse a lot, then I recommend the Razer DeathAdder 100%. It's on sale right now on Newegg for $44.99 and free shipping.
Personally, I'm not a fan of the bulkiness of Logitech mice, as I tend to lift my mouse a ton when playing FPS games. I went through three mice before I settled on one. First, I tried the Logitech G500. Love the feel, but it was way too heavy, and sweat tended to make it slip. Second, I tried the Razer Lachesis. Grew to like it a lot, but the laser causes it to move several pixels when you click down. Not really noticeable in games, but atrocious for web browsing. So I got the Razer DeathAdder; probably their most popular model. It was like heaven in my hands, but... it has no grip or dips on the side for leverage to lift it, so that was a somewhat difficult task. What mouse has the same shape as the DeathAdder, but it DOES have grips and dips on the sides to lift? Razer Mamba. The price tag, yikes. It's functionality is not worth that price whatsoever, but being the perfect mouse for me made it worth it, and the wireless turned out to be amazingly helpful (no drag from the cord).