If you're not the enthusiast who like to go to the track or involve in road racing where you need to use the brakes hard, the original brakes would do. You may want to change the brake hoses to steel-braided ones. These last longer than the stock ones and is more effective in delivering the braking power to the pads.
If you just change the panel filter to a performance filter and not do something to the exhaust, it's just like someone having constipation.. The car needs quick input of air (thru' the filter) to the engine for combustion and quick output. The stock exhaust has a cat which is quite restrictive to the airflow. Tkae this bugger out and replace it with a free-flow exhaust. If you don't rev the engine hard within 1st - 4th gear, and just cruise at high speed for long distances, the additional noise from the exhaust is quite okay. It's slightly more noisy than normal but Alfistis love to drive their Alfas hard to have the noise, especially boxers.