We are talking a lot of money and a lot of bikes here.. I suspect the difference in the frame is not the biggest change if getting the MU.

What about starting with different tyres for the Speed, or even a different set of wheels so you can leave the tyres on the wheels and just change from one wheel set to the other if you want different ride caracteristics?

Double chainring up front or dual drive wheel if you want more gears?

Or go to 10 speed on your current bike if you want.

I guess I am saying this becouse I am trying to downsize my own stable of bikes