Intel Core i7 6700 - RM 1305
Gigabyte H170-HD3 (D4) - RM 486
Corsair 16GB (8GB x 2) DDR4 2133MHz Value RAM - RM 324
Sapphire R9 390 8GB GDDR5 Nitro - RM 1549
Kingston HyperX Fury 120GB SSD - RM 209
WD Blue 1TB HDD - RM 215
Seasonic S12II 620W - RM 303
Tecware Alpha White - RM 229

Total: RM 4620 (ETech price inclusive of GST)

Since you aren't going for overclockable build (Z170 mobo), value RAM will do the job fine, this is because even if you get Corsair Vengeance 3000MHz RAM (for example), you will end up with 2133MHz only due to max supported RAM speed of non-Z170 mobo is 2133MHz only which is the base clock of DDR4 RAM module, so no point getting something expensive which you can't fully utilize the benefit of it.

Changing mobo to Asus H170 is possible with top up.

For sure the i7 which is having the hyperthreading technology (extra 4 threads) will have slight edge on gaming but not all games utilize this technology yet.

DX12 aims to reduce the CPU overhead and is believed can improve CPU utilization so i7 might become the primary CPU choice for triple A titles (even though many triple A titles recommend i7 now even in DX11 era, but it is still far from being able to fully utilizing the power of i7 though).

i5 is also good enough for gaming, get i7 only if your budget allows.

So you said you can upgrade the GPU if you go for i5 path, from R9 390 to R9 390X? Or R9 390 to GTX970/GTX980? GTX970 is slightly weaker than R9 390 though and GTX980 is more expensive than R9 390X.