From a renderability sense, focus on fill rates of the parallel processors, take the shader clock and multiply by the number of shaders. Generally higher the better -- but, since program performance is more than just GPU, you may not see the effect of that fill-rate being scaled. This is the mistake many make, expecting performance to be independent of a system's of components, program or prefered settings.
Your dual-core CPU is bottlenecking your GTX 480.
Unless the game(s) being played are more than dual-threaded, it doesn't matter what GPU is being paired, getting more cores won't do anything for the game. As long as the game isn't coded to use those extra cores, they aren't feeding the GPU any picture data. Thus, there is no logic in saying a dual-core CPU will bottleneck a GTX480. About the only thing we could say is if the CPU was at stock, then the user won't be able to enjoy higher frame rates and/or details as many who have their CPUs at higher speeds.
To those of you with more than duals and claim you notice a difference in your less-than-quad-threaded apps, what you are seeing is the effect of your other background processes using the extra cores while the game gets selfish with the cores they are meant to use. The game is not somehow using extra cores.
Let's say the OP was to get into modern/future games that eventually will be multi-threaded, is then a dual-core bottlenecking the GTX480? That depends on settings choosen, if higher details are expected, then more cores will feed the GPU better. That doesn't automatically mean lesser details don't need a GTX480. This is a common mistake/myth higher-end folks make regarding anything less that they prefer, they can't think in shades of gray.
Ultimately, it is perogative, and I for one am not going to assume we all have the same tastes in visual appeal or games. I don't know why people default to just their preferences when giving advice to others...
<message edited by lehpron on Wednesday, April 14, 2010 12:47 AM>