I will always recommend the full setup. You gain some future flexibility later on if your situation changes. For instance, whereas you already have a bunch of rails, you can take an existing 1400 rail and set up your new MFT 90 degrees off the factory setup for wider cuts. Or have the possibility of a full set up for different cuts or in multiple places at once. You can easily sell the extra parts (I know that I bought a set of extra parts used) if you later don't utilize them.
Peter