If you want to upgrade, buy some A-grade discs and upgraded pads (look into EBC, Pagid for instance), check if steel braided lines are availble and make sure the fluid is fresh (max 2 years old).
If your brakes are in good shape, but you lack brake performance, then investigate in better tyres. You can have the best brake discs/pad setup, but with shitty tyres, you will not be able to stop faster.