Does anyone know if it is possible for me to pre-order the expansion pack now and upgrade later? Specifically, is it possible for me to purchase the Collector's Edition for $49.99 then add the Legendary upgrade in a couple weeks when I have a little more money? Or do I just need to wait and make all the purchases at once? I'd like to pre-order now to get the Collector's Edition goodies, but I don't have the money for the Legendary upgrade at the moment.