If you want to control body roll upgrade the rear sway bar and get the front strut brace. If you want to lower the car or get a firmer performance orientated handling go for coilovers or lowered springs and uprated shocks like KYBs. Go to the Whiteline site they have a lot of articles on suspension, well worth a read. And remember the springs of a car are there to hold it up and cushion the ride in a vertical plane eg: going over a speed up. Swaybars are also springs but are designed to work in the horizontal plane eg: control body roll. If you use stiff springs to try and control the body roll it will have a negative affect on the ride quality, if thicker sway bars are used the the standard ride quality can be maintained with better body roll control.