i agree with them, grab a 2x4gb 1600 (just because they are so cheap and how much is 1333 vs 1600 nowadays?)
and yes upgrade your GPU, and please please, do not be fooled by gpu having 4gb of memory (like what you have) yet still at low end.
Think about it, you have 4gb of gpu memory but a 680 only has 2gb (usually). but in terms of performance, we won't even have to compare them.
Don't get me wrong, im not bashing you or anything, just don't be blinded by those. 4gb is useless for low end cards.