yeah 4 gb is plenty as it is i have 6 because i have an i7 and it just make sense to get triple kit i'm pretty sure even when i've never seen it go over 3.5 gbs used ever, and that's when i was running 2 folding at home clients, steam, itunes probalby 15 google chrome tabs, virus scan, advanced system care, smart defrag.
i'm asssumng you have a dual channel cpu if your asking about 16 gbs, if i were you just get 4gb is your want to really want to spoil yourself 8gb