Prioritizing Power Cable Upgrades by System Component.

I'm digging into the world of power cables and it is kind of amazing. The promise that a good cable can bring along with its price is both exciting and staggering.

There are several components that need some kind of power cable and upgrading them, for me, needs to be done in steps.

For those that have upgraded power cables, how would you prioritize between the pre-amp (tube), power amp (ss) and powered sub...and possibly even the DAC?