My belief is you should stick with a system. If you're looking to lower the vehicle, stick with Steeda components. I'm sure they've tested things together, rather than just putting out a larger swaybar (bigger isn't always better). For myself, I know the amount of engineering that various Mfgs put into police packages- it's an important market and those vehicles get tested extensively. For that reason, I'd roll with the PIU (police) shocks and swaybars- they use the same springs as the ST.
Of course, handling is subjective- you could "try" the steeda package with the PIU shocks. Who knows?