That's not the one I linked to, is it? Notice - X6800 vs. QX6700. The Q stands for quad core. Just because it's Extreme doesn't mean it's quad core. Read the specs on the newegg page - it says dual core.
Yes. Technically, you have a Core 2 Duo processor. Centrino refers to a bunch of parts, not just the processor, including the CPU, chipset, and the wireless adapter.
^^ Someone does real well in Intel's retail edge tests
But as a general rule of thumb with intel, if it has "Duo" in the name you can be willing to bet its a dual-core processor. If it has "Quad" in the name (like the Core 2 Quad) then you can be willing to bet it is a quad core. (this last paragraph of typing was information given to me by the intel rep for the store i work at. any problems with it and i'll get you his name )