I am going to upgrade my PC soon and was wondering if it would bottleneck with an FX-6300 and 2 MSI R9 270x's because my motherboard has 2 x16 slots, but one is running on x4 (Gigabyte 970A-D3P). Also plan on overclocking but is it good to overclock on a 970 board or should I get another board thats a 990?