The only upgrades I've done to my G17 are the following:
Steel guide-rod (makes it easier to tune your springs to your ammo load)
Vickers Tactical Slide Stop
Factory extended mag release (dehorned by me)
3.5# factory disconnector, 8# NY trigger spring
I would avoid reduced power striker springs.  I've experienced too many light primer strikes with them.

Mark

Mark
A07211
downrange360.blogspot.com
Unrepentant IDPA purist

"Nine targets isn't a defensive scenario, in my book, that's combat."