Ultra scope and SDI input

Been thinking of picking up a ultra scope (pci) for a few months, just have a few questions for those who own one or know about them.

Is the SDI input the only way to feed it a signal to display? Does that mean I need to loop the output of my decklink to the input of the ultra scope? Also I'm running 2 monitors on my mac pro, and still have 2 free DVI ports, is it as easy as adding a third monitor and using that as the output of the ultra scope?

I searched for answers and am still confused. I'm also tempted to just pick up a Tektronix or Videotek HD-SDI vectorscope/waveform combo just to save a pci slot.