Watch for sales on Ultegra Di2; it works just as well as Dura Ace, and it's a much better value, as long as you're happy with a 10sp cassette (rather than 11). I understand the components are also interchangeable, so you can always upgrade, especially the parts that stand out, so that it's harder to tell if it's DA or Ultegra. Not many people can tell the difference, anyway. Even fewer care, unless it's on their own bike!

Luis