Assign a process to 1 core....is it possible?

[muzicman0]

I'm planning on buying an Intel Q6600, and am wondering if it is possible to assign an application to run on one core? For instance, I would love to assign 1 core to my virtualbox install. If I can't, then my question would be, would I be better off getting a 2.4 Ghz Quad core, or a 3.2 Ghz Dual core?
mm0