Be careful Matt - the biggest single factor on stopping distances is actually the tires that are on the end doing most of the stopping (the front in your case), not the brakes. Bigger brakes are great on cars that are going to be tracked regularly. However, for street cars that need good brakes for that occasional hard emergency stop, big brakes do very little. If your stock brakes are capable of locking the front tires, then they're capable of holding the front tires on the limit of their adhesion for one stop. Big brakes will do little to change that. Where they will help is in repeatability - because you'll have the ability to repeat that stop over and over. The stock brakes will heat up and fade away after a stop or two.
Many magazines have done objective tests on this (that is - the magazine actually did the test, not the company selling the brakes!) -- if your brakes will lock your front tires now, there's little improvement in stopping distance that will come from putting bigger brakes on. The discs on the rear are cool - but the rear brakes do very little of the work of stopping a stock suspended car because of all the weight transfer to the front.
If you've upgraded wheels and tires (more traction) you may have more traction available than stock - and that can overtax stock front brakes. So, some testing may be in order - have you done any threshold stops in your car with your stock brakes? See how they perform - if they'll hold the front tires on the verge of lock up for one stop - then bigger brakes (with your same tires) won't significantly shorten your stopping distances.
If you're gonna track the car - definitely consider brake upgrades - bigger rotors and matching calipers, stainless lines, fluid, pad selection and cooling are all important. Just don't forget at anytime during the process - the brakes stop the rotor -- the TIRES stop the car.
