PCIe 3.0 or not the difference will be really negligible as you said 5fps absolute worse case scenario and it directs back to my original question of what you meant by saturation I was talking about whether the lanes bandwidth is fully used or not, not the difference between PCIe 2.0 to 3.0 for a current gen gfx card. It's the same boat as going from SATA2 to SATA3, depending on the controller used, JMicron, Marvell or the Intel onboard the difference is sometimes really small, sometimes can be big.