When it comes to PC's the motherboard and the CPU are *THE* heart of the system. Skimping on things at this point will hurt the performance of the entire system.
I would also recommend replacing the video card with an AMD RX480 8GB for $22i9. These cards will be released on June 29th, and will compete with the GTX 980. AMD has been building these cards for awhile now, in an effort to try to avoid having the stores run out of them. These also only need a single 6 pin power cable.
I took the liberty of selecting a lower end Intel i5 CPU, a lower priced motherboard, added a 1TB hard drive and a 550w Power Supply. I wanted to put the RX480 8GB video card, but since they will not go on sale for another 7 days, they are not showing up in the lists yet. So add $229 to the price you see at the link below to cover the cost of the AMD RX480 8GB video card.
http://pcpartpicker.com/list/3D48KZ
I hope this helps you out.