Choosing RAM for purely gaming: Latency or speed?

Hi,

I'm updating my rig and got all the parts decided except memory. I've chosen G.Skills Ripjaws X -memory modules but I'm bit confused which one I should choose?

2x4Gb DDR3 1333 7-7-7-21-2N 50€~67$
or
2x4Gb DDR3 1600 9-9-9-24-2N 46€~62$
or
2x4Gb DDR3 1600 8-8-8-24-2N 66€~89$

As mentioned in the topic, this will be purely for gaming. So is the performance worth the higher cost? In the end it's not much but why pay 20€~27$ extra for practically nothing? And what about the 1333 with CAS 7, instead of 1600 with CAS 9?

My rig will be:
CPU: Intel Core i5-2500K
GPU: Radeon HD 6950 DirectCu II, 2 GB
MOBO: Z68 Extreme3 Gen3