The only LGA 1155 board the I have been able to spec out with dual 16 x 16 PCI lanes is :
http://www.asrock.com/mb/Intel/Z77%20WS/index.us.asp?ca.... There are several choices for dual 16 X laned motherboards in LGA 2011, but that is a different platform, with more PCIe lanes. The only reason that the ASRock Z77 WS can use dusl 16 X lanes is because of the PLX PEX 8747 bridge. Normally the LGA 1155 chipset is limited to 24 (or 23) PCIe lanes and you need a bridge chip to get more. Look at this discussion for further info:
http://www.overclock.net/t/1267524/how-many-16x-pcie-sl....
Also, as I understand it the PCIe lanes are limited to the 2.0 rather than the 3.0 spec. So you will have to await new designs for a LGA 1155 to use dual PCIe 16 X at the PCI 3.0 spec. As the IB platform is coming to eol status you may need to go to a Haswell CPU for dual PCIe 16 X on the 3.0 standard.