The small amount of fuel saves on precious weight. If you ever wanted to make the Integra a full fledge road course race car, here is a very good example of the things you'll need to have done to your car. The springs lower the center of gravity of the car and the slightly stiffer rates minimizes body roll while still maintaining a decent ride. To save money, you can replace the stock shocks at a later time when they wear out. The Yokohoma A509 provides very good all around performance with a nice price tag.
Engine performance increases due to the increase airflow and reduced pumping losses.
The 7 inch wheel width is a better match for the 205-50ZR15 tires. Handling will vastly improve over stock due to the superior tires and lighter wheels. The upgraded ignition system is necessary when the spark requirements increase due to increased airflow. With all the horsepower that you have, you'll need the ability to come to a stop quickly and fade free. Slotted brakes does the job of removing gasses, while not reducing braking surface area.