nvidia and amd overstate their psu requirements in case you've got a gutless wonder psu that can't deliver its labelled wattage. that build should consume around 420-450w at full overclocked load with an overclocked i7, so a good 500-550w unit will be more than sufficient.
hardocp.com/article/2015/09/21/xfx_r9_390_double_dissipation_8gb_video_card_review/10
overclockers.com/msi-r9-390-gaming-8g-video-card-review/
on top of that, consider a few changes to your build to increase cost-efficiency:
pcpartpicker.com/list/dhkRGf
cpu overclocking doesn't increase gaming performance all that much compared to how much you have to pay for it. this locked i5 has a low base clock speed but you can set all cores to 3.3ghz via turbo frequency tweaking in bios.
an expensive mobo and cpu cooler won't be necessary if you go locked, you'll just have more ports and miscellaneous features that you'll likely never use
the 850 evo is fast but is overpriced to hell in the us right now. planar tlc drives like this corsair have theoretically (not in practice afaik) lower lifespans and long sequential writes are slower, but otherwise you won't notice a difference in day-to-day usage. also consider getting a single 500gb ssd instead of 240gb + hdd
the just-released rx 480 is equal to/slightly faster than the 390 while also being cheaper and more power-efficient. grab a gtx 1070 or used 980 ti instead if you're willing to shell out more cash.
case here is cheap as shit, but comes with two fans and will fit all your components with no problems.
the evga g2s are among the best psus you can buy, but a 520w seasonic will perform almost as well for about half the price. consult professional reviewers like jonnyguru for more info about both units and ignore any tier lists you come across.
lastly, i've upgraded your monitor to a 1440p 144hz freesync model. if you go for a 1070, get something with gsync instead, like the dell s2716dg.
