r9 280x pcie 2.0 or 3.0/ vapour x vs dual x

[Rampy]

iam going to buy the r9 280x vapour x (saphire radeon). And the mother board is asus M5A97 evo R.2 which has pcie 2.0. will the performance of r9 280x will be slower if it is installed in pcie 2.0 than 3.0 or the performance will be same in both?

second question is: approximately how much difference will be noticeable between dual x and vapour x of r9 280x?
please helpme

 

[Conrad Pinto]

In gaming, there is no performance difference between 2.0 and 3.0.

 

[Eduello]

There is really no difference between PCI-E 2.0 and 3.0. And the difference between the dual x and vapor x is like ~2-3%.