Duo vs Quad?

I’m pondering which processor to chose for my new build, and I’m lost as to whether I should chose the core 2 duo e8400 or spend $20 more on the core 2 quad q6600. My level of tech savvy basically tells me that A. 4 > 2, and B. you get what you pay for. So will I notice a difference between these two processors, or are they more or less similar? If there is a difference, is there a specific instance that I will lose performance if I go with the duo? Mainly I’m going to be using this machine for college programming projects (VB.NET, C#, that kind of thing) and maybe some light gaming.