According to the Steam requirements, the minimum is only 1.8GHz dual core - so you might not be able to max out the detail, but I'd expect it to run fine on lower settings.
The game uses PhysX, and your NVidia card can do hardware PhysX accelleration. If you haven't tried it, it might be worth experement with the PhysX settings from the NVidia control panel ("Set Multi GPU and PhysX configuration" section) - try forcing it to your graphics card or your CPU.
As for resolution, what kind of monitor do you have? I'm guessing a 16:10 (1680*1050). In that case, the lowest you can drop is to 1440*900 to avoid the black bars, but you might just have to bit-the-bullet and drop lower (maybe even as low as 1024*768) and put up with the black bars.
The game uses the same engine as Fallout 3 and Oblivion - did they run OK on your system, and if so at what resolution? Being the most recent, DKS probably pushes your machine harder than the earlier two games, but it might give you a reference point.
