Are you starting to run out?
16gb is a lot of ram. I usually add more when I see my ram usage go up over 50% when running apps, just to make sure I'm out of that damn pagefile.
Just keep in mind it will put more strain on the imc and can limit overclocks. 4gb is bad enough I would hate to see what 16gb does.
I know with my system having 4gb drops my oc by ~200mhz compared to 2gb.
Back in the old days when 16mb was the go my work gave me a system with 40mb installed and it was no faster/smoother than a similar system with 16mb.
16mb sounds funny now.... I nearly wrote 16gb and thought that wasn't right.