If I buy a dual core I might. How much does a dual core cost? A quad core?
Folding At Home is something which is (allegedly) a useful thing to do with your spare CPU cycles. The ones available in the system you have now that you already paid for. It might or might not produce anything useful but it's supposed to be a good thing to do because it doesn't cost anything to use existing computing capacity. If you get obsessed with league tables and scores and you are considering spending mucho $$$ just in order to complete some "target", then, if you don't mind me saying so, you are missing the point.