I concur with the above. 2 pounds is negligible and the importance of weight is often vastly overstated.

I would also say I can't think of too many reasons why either the Wilier or Focus will give you much of a performance edge over the Defy, unless you change the setup (especially the rider position, wheels and tires). This is not to say that getting a 2nd bike is necessarily a bad idea; just keep in mind that it won't really make you faster.