The build looks good, that is a great motherboard + processor combo, you should consider overclocking, that CPU overclocks very nicely. As far as the RAM goes, you didn't put a price limit so I am assuming it isn't a huge issue. That motherboard supports tripple channel RAM so you want triple channel to take full advantage. 6GB will be enough for almost any applications so here I would suggest:
G.SKILL PI Serieshttp://www.newegg.com/Product/Product.aspx?Item=N82E16820231335
It is fast and mid-line expesive.