Just get some 8gb (2x4gb) 1600mhz ram and call it a day. Gaming doesn't have much to do with ram. Honestly 99% of the brands out there are good G.SKILL, Corsair, Crucial, Mushkin, Kingston, Samsung. There are a lot of other ones but they aren't that well know to most people so just get it from one of the brands I recommeded. RAM doesn't even produce much heat, most "stylish" ram, so the heat sinks, are just for aesthetics. If you are just gaming 8gb is the sweet spot. Finally no, it does not have a "big effect" on gaming.