The Gigabyte A75M-UD2H comes with two PCI Express x16 slots, one PCI Express x1 slot, and one standard PCI slot.
The first PCI Express x16 slot is connected directly to the CPU integrated PCI Express controller, and it always works at x16 speed. The second PCI Express x16 slot is connected to four PCI Express lanes on the A75 chipset, so it always works at x4 speed.
If you install a dual-slot video card in the first PCI Express x16 slot, you will “kill” the PCI Express x1 slot. If you install a dual-slot video card in the second PCI Express x16 slot, you will need a case with more than four expansion slots (several SFF and HTPC cases have four or fewer expansion slots), and you may block the headers located at the motherboard edge.