I am planning to change a Cannondale Alloy Synapse 5 105 triple (50/39/30 crank set) Synapse 5 to compact 105 double (50/34 crank set). I know I will need to change the crank set and FD (want to use 105 components). Do I need to change the Shifters as well from ST-5703 to ST-5700. My ride is 4 years old and price is a consideration. Saving $'s in this change would free $'s for later to a 11 spd ultegra future bike purchase. I hope that the 105 RD-5700 should not require changing. Perhaps this change could add new brake calipers as currently have Tektro R539 brakes, upgrade to 105 or Ultegra brakes?