I would say probably. Certainly windows can run dual monitors from dual graphics cards.
But it just might depend on how the motherboard handles a plug-in card when there's already on-board.
Try it and see - you can't do any harm.
In the BIOS there is normally a setting "Init graphics (or display) first" - this sets which card is selected first for booting up, when the windows software has not yet loaded.
Don't forget you will need both graphics drivers loaded.