lets have a look at your current specs - shall we?
6GB is actually a silly idea...with dual channel mem in effect from a ong time - you would either get 3x2GB sticks which nulls out the feature of dual channel mem architecture.
if you get 2GB sticks then you can have a minimum of 2GB in only one slot or 8GB on all 4 slots poulated
3GB sticks aren't (yet) made.... so its either 2/4/8/16
FYI - for most games now, getting anything above 4GB isn't fully utilized - i can't find the link but you could do a google search of the maximum ram utilization...add that with an OC as well...so you can see a limit to how much you can actually use in real world apps/work
BF3 huh? like i said, lemme see the specs of current rig and maybe we can handle it a lil differently.
waiting can be a PITA - but when you pull the trigger with teh right parts - you're happy a fish in the sea