16GB Ram ??? I haven't see any game will use all 16GB ram... if you are not use Windows 7 64 bit version... even 6GB also good enough... (32 bit windows cannot locate more than 4GB ram)
I think you better spend more $$ on graphic card rather than RAM will be better (if just for game playing)
BUT very very important thing is... the power supplier.. I think at least 800~1000 W |