the jcw kit is a supercharger reduction pulley, cold air intake, catback exhaust , larger injectors, a slightly ported cylinder-head, and software.
aftermarket would be pulley $130, intake $230, catback $900, injectors $300, head $1500, software $500-$800 for 3,560-3,860
the aftermarket will also make significantly more power

for a nice upgrade do the pulley, intake, exhaust
or if you're content with stock power you can just drive it the way it came and have lots of fun