It's not even worth moving from 4 to 8 unless you can establish that you currently are using all of the 4 you now have.
More RAM isn't going to magically make anything faster in and of itself.
Very few people use all of 8 and thus might need 16.
I rarely if ever use over 3 so don't want more than the 4 I now have.
You would get much more bang for the buck with an SSD if you don't yet have one.