Two different video cards in one system unit?

Question

linux

Hello!
I got a second video card for free, the characteristics are almost identical, it's a pity to put one of them on the shelf. Is it possible to use two video cards connected to the motherboard? Will they improve performance? Working not in SLI mode.
Asus motherboard p8z77-v
PSU 700 W
First card GTX 760
Second card HD 6900
OS Ubuntu 14x64

Answer 1

Depending on the graphics drivers used, I recommend:
1) For open firewood - AMD
2) If you don't mind installing proprietary ones - Nvidia
Installing two makes sense only if you have a virtual machine where you want to forward a physical video card for games. Otherwise, with ordinary use, the second will be completely useless.

Answer 2

you can connect multiple monitors

Answer 3

This is no longer relevant, something will have to be abandoned