My two cents - yes, a Core2Quad is sufficient to run this game with decent performance. What is more important is your choice of graphics card since CloD seems to rely heavily on graphics memory (VRAM). Despite what it may say ‘on the box’, I would consider 1GB of VRAM to be a minimum for decent looking graphics. Have a look at this
post by FS~Phat examining VRAM usage and you will get some idea.
Although I don’t currently have access to one of these cpu’s, I recently did some performance testing on my daughter’s pc using a Core i5 750, Radeon HD5850 and 8GB memory, and found that it would run fluidly as long as the graphic settings were not set too high. As soon as the settings required more than the available VRAM (1GB for this card), the stutters would start becoming apparent. Using a utility like Bandicam could allow higher settings than without, as with a bit of tuning you could get the frame rate to a point where it would be fast enough for viewing, but slow enough to mask the stutters resulting from excessive VRAM usage.
To dodger; I assume that you currently have a dual-core – a quad will give you a decent performance increase as CloD is multi-threaded (it uses all 8 on my pc), just don’t expect to be able to run very high graphic settings unless you have a graphics card with 1.5 to 2GB of VRAM. It will definitely improve the ‘fluidity’ of the game compared to a dual-core.