A Canolite D is a bad choice for the X100. High sync voltage will eventually (if not instantly) fry the camera. It also has no autoexposure circuitry (all it does is trigger flashmatic aperture operation in the camera).
An isolator with a Vivitar 2800? Mine shows 36V sync voltage. Probably not a good long-term choice but not the 100-300V Vivitar 283s of yore.
I would highly, highly recommend a Nikon SB-30, not in the least because it has a 4.4v synch voltage and can actually be used off camera using its built-in slave function (the X100 main flash can trigger it).
Dante