Psycho is saying that more than 8GB doesn't make any difference for him, He may not be using his PC for the same things your using yours for.
He didn't say, upgrade to 8GB of RAM.
You will get no benefit from adding more RAM to your PC as your PC doesn't use all 4GB you have now. It would just be a waste of money.
I use my PC mostly for gaming and I only have 3GB of RAM but its still enough.