I currently have a Sora 3 x 8 sp STI group on my road bike that is going to be transfered to a modern frame - however, my LBS has an Ultegra front/rear derailluer set that I can pick up for $90. Is it worth buying the derailluers only and upgrading shifters at a later time, or should I wait and upgrade all at once? They have a set of Ultegra shifters as well, but they are triple, and I want to move to a double up front, so my plan is to wait until I am ready and get the rest of the drivetrain when I am ready for that.

I have my decals and am taking everything off of the frame this weekend, then off to the powdercoater.