How is this PC build?

Solution
OCing your CPU will be no problem with this setup but the 970 will struggle from time to time with quite a few games @1440p if you want them to run at high/ultra settings. You would need a second 970 or a 980ti to do this without any problems, especially in newer or demanding games like GTA V, Shadow of Morder and so on.
But it will do okay at 1440p with most games if your lower the settings a bit. But in generell it will be totally fine and will also run any games from 2014/13 or older at max settings i guess.

Only thing id change is the PSU, not because of it's quality, but because of the 620w which is quite alot for this system but not enough for adding a second 970 after price drops in the future for example.
If you want to stick...
OCing your CPU will be no problem with this setup but the 970 will struggle from time to time with quite a few games @1440p if you want them to run at high/ultra settings. You would need a second 970 or a 980ti to do this without any problems, especially in newer or demanding games like GTA V, Shadow of Morder and so on.
But it will do okay at 1440p with most games if your lower the settings a bit. But in generell it will be totally fine and will also run any games from 2014/13 or older at max settings i guess.

Only thing id change is the PSU, not because of it's quality, but because of the 620w which is quite alot for this system but not enough for adding a second 970 after price drops in the future for example.
If you want to stick to the single 970 just go for something like 500w and if you want to add another one 750w should do fine. :)
 
Solution
AMD FX-6350
Gigabyte GA-970A-UD3P
8GB (2x4GB) DDR3 1866
Combo Deal: $238

Corsair SPEC-03 Gaming Case: $70 before $10 rebate
Samsung 850 250GB SSD for $80 with code AFSAMSSD928B
Asus Radeon R9 390X: $400 before $20 rebate

Win 7 64-Bit - OEM is $80 with code EMCAXPA24 ---- promo code ends at midnight on 10/1

8GB of RAMs should be fine ---- you listed 4x4GB in your build. At 1440p your gaming is more highly dependent upon your GPU and less so upon your CPU.

If multiple video cards is your plan, you need a bigger PSU, and a combo like this for $310 before $10 rebate ...
AMD FX-8350
Gigabyte 990FX -UD3
HyperX Fury Black 8GB