Are you unhappy with the way your computer works or are you just taking what pc pit stop tells you as Gospel?
If you don't have any real problems with your machine (machine, not Internet speed) then I would leave things alone.
Regarding you Internet speed, that is dependent on your supplier. Upgrading your computer will not improve it.
You can cause all sorts of problems messing about with a computer trying to improve its performance. Very often you end up with a machine that is a shadow of its former self.