ok, the way a spring/damper system works...
you drive down the road and hit a bump, the bump pushes up on the tire and through the wheel and suspension it ends up pushing up on the spring. you know simple physics states that every reaction has an opposite but equal reatcion right? since the spring can "give" it gives and pushes back down trying to return to its original state. just for your info, the wire that forms the spring actually twists when the spring is compressed, that's what causes the spring action. ok, well the spring then shoots back with this stored up energy from the bump and over shoots its original position and over extends. once it gets there it tries to come back and over compresses but less this time since it has wasted the absorbed bump energy moving back and forth.
the point here is the spring will just sit there and bounce back and forth until eventually it settles out. think about dropping a bouncy ball on a hard floor and watching it slowly bounce less and less.
now, the damper lessens the effect. the damper is like placing a pillow under the bouncy ball. the ball may bounce up once but then settle down in the pillow. if the pillow is too soft the ball won't bounce at all and if the pillow is too firm the ball may bounce too much. you want the two to match just right.
so, you want the springs to match your shocks. if you get shorter springs you need to retain the same spring rate (rated in pounds) of your original springs since these were matched with your shocks. depending on how old your shocks are, it may be wise to replace them as well.
a performance oriented spring/shock combo compromises ride comfort. i wish i would not have upgraded my DX to a sports set-up. my Si had a nicer ride with its stock springs and shocks. oh well.