Bump steer kit or X2 Ball Joints or??

OK Im running Sportline springs (luckilly the rears aren't sagging...yet) and sometimes it seems if I hit bumps or good expansion joints on the freeway the car wants to turn on me. Should I get a bump steer kit? Or X2 ball joints? I like to push the car in the turns and plan on some auto-x and open track stuff. Im wanting a predictable car I can be confident in while driving. Also how hard is it to install these parts? So far Ive done every mod om my car myself except the gear instal. I know I will need to get front end aligned afterwards.