Hi, I suggest you to install Collusion extension for Firefox, which let you know which websites are tracking you, this is very important.
Then, you can install also Auslogics disk defrag, which can speed up your PC.
I agree with
@saket because an anti-exploit is fundamental in a security configuration.
In addition, you can also install MPC-HC, which is a very good media player.
For the rest, it is a good config.