What should my next upgrade be?

[Whagwan]

Hi all. Current System as below:

i5-2500k @ 4.5Ghz
H100i water cooler
Gigabyter GA-Z68X-ED3P board
8Gb Corsair Vengeance DDR3 RAM
GTX 970 GPU
Loads of SSD and HDD space.
Game at 1080 60htz

It's bonus time and I'm expecting a kid next year so probably won't be able to upgrade again for a few years.

I can probably spend £200-£300 tops.

Is there anything worth doing for this kinda cash that I will see a decent improvement on or is this too much of a step change?

 

[SkyNetRising]

You could upgrade ram to 16GB.
GPU upgrade also might be feasible. GTX 1070 perhaps? But that will require more than £300.