Yes a stiffer ski does give you more pop off jumps and a more stable landing. However the stiffer you go less forgiveness in your skis.
If your looking for a good jump ski just make sure it's full cambered, no rocker. Detune to your liking.
I would say spend your money on a good fitting boot with some type of footbed. Get a proper fitting boot and go from there.
You could also find some nice used stiffer skis that have been softend up, in the for sale forum.