A gtx 390x isn't enough for a good quality 4k experience and I very much would not recommend it. I think you'll be more than satsified with a good 1080p 144hz monitor. At the same time a gtx 980 is completely overpriced and horrible value for its performance. You were better off with the 390x. You can also save a bit of money on the psu.

This build is much better for your needs and has much better upgrade-ability. You can overclock this build, and if it interests you I highly recommend it. It's fun overclocking a pc. Also, room for 16gb of ram if you want it.

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