It's going to cost you 2-3x as much to get a mobo like that. LGA 1155 is the best socket for gaming. Besides, x8/x8 and x16/x16 has no difference, maybe a few %.
If i change Radeon HD 7850 to GTX 570 2.5GB & use Core I7-2600K, then i don't need PCIe 3.0
cuz GTX 570 & 2600K don't support PCIe 3.0
in this case what is the MOBO that has PCIe 2.0 dual x16?