Two different cards, two different monitors

I have searched for this and only found old results. From around 2007.

I have a GTX 560ti, Radeon 7950, and a GT520. I plan to display to 3 monitors with the 7950, but I would like to power a 4th monitor. Could I use the GT520 or GTX560ti to do so or am I forced to purchase another 7950 and run in a crossfire configuration?