hello, well ive heard that pcie 3.0 doubles the tranfer rate of pcie 2.0, a MOBO that dont support 3.0 will limit the video card, as well the processor must support this feature, so imagine u get a pcie 3.0 video card and install it into your MOBO it will run good enought but it wont max, i think im in the correct, right now the recommendable MOBO and processors are from intel, they support this feature Z77 chipset and ivy bridge processors too, but of you have a MOBO then pick the pcie 3.0 card cause no one knows maybe in a while you change your mobo and processor and you will have the video card with you you see.
well pcie 2.0x16 and pcie 3.0x8, it wouldnt be almost the same i mean if 3.0 doubles the transfer rate 3.0x8 would be like the x16 on pcie 2.0, but right now im not sure my friend.
ive understood that in pcie 2.0 a lane is 500MBPS so 16x lane is 8GBPS vs pcie 3.0 a lane is 985MBPS 16x 15760MBPS,
it would be almost the same in the question u asked, 2.0x16vs3.0x8.
i think its recommendable to get a pcie 3.0 mobo, you can get the full performance the video card can bring and dont forget that the processor has to support it as well, oh i checked and yes nvidia 700 series will feature pcie 3.0