I want to upgrade but right now I can only upgrade my video card. My pc has onboard video and it doesn't look like it has additional slots for a new card. I've looked online for external video cards, but the way people talk about them leads me to believe that these external cards are only for additional monitors, not the primary (and only) monitor. Is this true or can I use an external card if I only have one monitor? How can I tell if the card is directx 12 compatible or not?