Unless that u work with many adobe applications at the same time the 8GB will be a waste of money.
In systems with dual channel architecture 4GB is more that enough for the games and applications that exist today and the recommendable for any rig. For system that support tri channel architecture the most common are 6GB.
For example exist some 2000MHz with CL9 with a high price, but if u compare that RAM with a 1600MHz CL7 u get the same or maybe better performance with the 1600MHZ and with less price.