lowering springs with cup chassis

hi im thinking about getting some -30mm apex lowering springs from k-tec but with the cup chassis am i going to see much of a difference, because i seem to remember the dealer saying that it is lower than the standard chassis?!

I just want it sitting a bit lower but without messing around to much with the comfort!

anyone shed some light for me?!
 
thought the stiffness was in the shocker not the spring thats why when you fit after market springs on cup suspension it make it really hard.