Pci-e v2.0

[mgartner]

What would be the best video card to run Premiere Pro on an older
Asus p7h55 pro mobo.. it has 8 gig ram and i7 2.93g hz. (820).
Will some pci-e v3.0 cards work on it.?

[David (PassMark)]

All PCIe 3.0 cards should fall back to PCIe 2.0 speeds if that is all the machine supports.
If this is only for Premiere Pro, search the web for this specific software being used as a benchmark. Someone might have done some testing on various cards.