The compatibility chart is awesome.
Shifters: Shimano Ultegra Di2 6770, Electronic
Front Derailleur: Shimano Ultegra Di2 6770
Rear Derailleur: Shimano Ultegra Di2 6770
It looks the above is what I need if I go with all electronic route. I don't see a whole lot of info on Giant 2013 Defy Advanced 0 to decide if I could use manual shifters. I am still trying. Thank you.