You do not need PCI-e 3. 2.0 will work just fine, even if the graphics card says its 3.0.
Just 3 things you should consider.
1. DO NOT overclock the CPU on that motherboard, its not designed for it.
2. Try for 2 x 4GB RAM for a total of 8GB.
3. There are better power supplies, I usually suggest avoiding those builder series units.