Cheapest:
Polish internals
13# hammer spring
next level:
Polish internals
11.5# hammer spring
extended firing pin and reduced power firing pin spring (need this when you go below 13# hammer spring)
Reduced power trigger return spring
Best option:
Polish internals
11.5# hammer spring (or 8.5# and federals only)
extended firing pin and reduced power firing pin spring
Reduced power trigger return spring
CZC Comp Hammer
CGQ adjustible sear