Question: Did you make sure you cleaned the DBA rotors before putting them on. I know mine had quite alot of oil on them when I installed. I decent brake cleaing product and a clean rag clened them up nicely.
I have exactly your setup. And my braking performance is now *better* then when I bought the car, that said initial bite does feel a bit less than stock but the stopping power is definitely there. No spongy feeling from the pedal either. Did you change brake fluid when you put the new rotors on?