Originally Posted by bringler26
Spring rates are most likely different. The prokit likely will not be as stiff as the sportline. Generally shorter springs are stiffer.
^ this. The Sportlines have a higher spring rate to compensate for the reduced travel. The advertised drop is .8" for the Pro Kit and 1.5" for the Sportlines, approximately. New sets come with springs, bump stops, and rear dust covers.
As for replacing the struts/shocks, you may want to hold off on that for a little while because the only aftermarket set right now is pretty expensive. Many members are currently between 20-30k with no perceived problems with the OEM pieces. If you really want upgraded shocks/struts, order a set of ST struts with Ti HP shocks from either Village or Tousley.