I'm looking to upgrade braking performance. Is it cheaper to get a kit or piece one together by myself?

What pads are good?
What rotors are good? Do I need rotors for all four corners or just the fronts? Do I need new calipers?

 

When you buy a kit, you're paying for the huge rotors and the multi-piston calipers, in many cases, also the name (Brembo, Shelby, etc). If I could afford another $3000, I'd have a big brake kit for sure.

I just bought some Cenrtic dilled/slotted rotors from BrakeDesign.com and some Hawk pads from Summit (they're local for me!) for the front and rear. I really only bought the rotors for looks, but I know Hawk has great pads. Also didn't want to re-use the stock pads with over 20,000 miles on them.