HRFranklin0702 :
Herc08 :
i5-7500, and then a i7-7700.
That's probably your steps. Skip the i3. What else do you got? No need to upgrade the CPU if your GPU isn't changing.
I'm thinking of an RX480 maybe but I'm not sure yet
If you can, wait for Vega. You will be hard press to try and find a RX 570/580. They say it's suppose to be released at the end of July, but without a price or spec sheet, I'm a bit skeptical. However, prices of the RX 580 may go down if Vega does come out and it's out of your budget. So either way, it's a win-win.