Generally speaking, to run basic applications all you need is a dual core CPU. Programs must be designed to use multiple cores otherwise it will just default to using a single core.
For example, I read somewhere that the Sims 3 only uses a single core. Is that true? I dunno, someone would need to buy me a copy so that I can see for myself. If you are using an 8 core FX-8350, then it will only use 1 core.