Can you lock up your brakes or cause the ABS to kick in easily? If so the best pads won't do squat to help stopping distances. Pads stop the rotors, TIRES stop the car. Do you have some good rubber on the car now? If not, you will notice a difference in stopping from that change. Increasing rotor size will not necessarily make you stop any quicker. Pad compound plays a big role, assuming tires are up to the task. Large rotors are good for preventing brake fade from heat build-up not much good for decreasing stopping distances.
Oh, and stop tailgating! If you are worried enough about rear-ending someone to look into a brake upgrade you are driving way too close. Yes, I am serious.
/bill