Graphics Cards

[FlyingFrog76]

Thanks. 

[goodplay]

From a pugetsystems article,

[ScotchFury]

No. 

Most video cards don't get near maxing out PCIE 3 bandwidth.  Even the current high end GPU's have minimal performance difference between 3 & 4.

Also PCIE 3 cards in 4 capable slot just run @ PCIE 3.

[FlyingFrog76]

They are interchangeable with the only difference being that with the latest generation GPU may crash at 100fps or more in a PCI x 3 compared to x 4. No difference in FPS.. zero diference. 
May be differences in space between things with the motherboard when you socket it - maybe