I hope it isn't too late for me to say something helpful. I really like where you're going with Duke. Duncan Thomas and Elizabeth Frankenberg are now in Duke and Thomas is the head of BREAD -- a really cool organization of development economists. It'll be great to go on to the PhD in Econ right after that.
Am I too late to jump in? Paying out a lot of $ for SAIS is not necessarily a good idea given the economy now. LSE and HEI can give you the same value in terms of networking opportunities. Also European programs give you access to different types jobs related to International Affairs.