Thanks for the advices.
and thank you for noticing my CPU upgrade, Macsonic.
If I am not going to gain much, I should stick to what I have currently.
I only do light photoshop and video encoding/DVD ripping which I believe uses more CPU power than RAM.
I guess if I am going to upgrade, I should go 3 sticks, than 2 sticks right? so 3 X 8GB?