When using multiple graphics cards, the PCIe slots do not operate at their full bandwidth. As with most other motherboards, the configs for graphics cards are:
16x, 0x, 0x
8x, 8x, 0x
8x, 4x, 4x
This is listed in the specifications for the board on their site.
I actually ordered the Gigabyte Z97 Gaming 7 today to replace my MSI Z97 Gaming 7 that I received yesterday due to the fact that it has better power phases.