OK,it's very doubtful that you could install a new E6800 in your PC and have it work. Your CPU is 65nm process,while the E6800 is 45nm. The 45nm CPUs require at the very least a BIOS update, and more likely another board to be utilized.
A CPU upgrade or overclock, doesn't really yield what you're expecting. You might get a 10% increase in system speed for a 30% overclock. And just bumping the CPU up a notch won't do a whole lot more than squat.
In a prebuilt PC, generally CPU upgrades are offered in the form of a package, along with more RAM, and a larger HDD. The CPU is rarely offered by itself.
Dell, (and other makers) will generally only offer BIOS updates to the extent of the CPUs that this PC could have reasonably been expected to ship with. So, you might be able to install a quad, but it most likely would have to be from the same era as your C2D is, (Q6600 or better). A core 2 quad wold only offer performance increases with respect to certain software, mostly video rendering, image processing, and maybe a few games.
That said;
.i'm not sure if i can install the new Intel i7 line of processors?
Ryan, someday you'll look back on that statement, perhaps fondly, and realize how silly it was. For your sake, I hope that someday is soon.
In the mean time, would you like to borrow my sledgehammer?