^This is your answer. Basically buy whatever frame you like because your Ultegra crank can be used in whatever frame you choose. You may need to use a different bottom bracket than what you currently are running but that is a simple matter of buying the right one for your new frame if necessary. You may be able to use the same bottom bracket you have now if your new frame has the same type of bottom bracket shell as your old frame. The BB shell is the portion of the frame that holds the BB.