Displaying Same Smart SDR Screen on Two Monitors at the Same Time

I really have looked and can't seem to find this answer so forgive me if it has been asked and answered before. I have a Flex 6400 (not M) and what I am trying to do is display my Smart SDR screen on two different monitors. Essentially one for me while I am operating and one for guests to see what I am doing. I have a new video card which has two free outputs (the card has 4 outputs, three display port and one HDMI). I am using two of the three display port outputs and would like to add an additional monitor for this functionality. I am hoping this is possible without adding additional hardware. That said, if additional hardware is needed, what might that be? Please remember that the 6400 does NOT have the HDMI output that the 6400M does. Thank you all for your time and patience!
Fred - KF4FC