Power cord heiarchy

Would go with number 1. Since that feeds everything else, better power to it, should give better power to everything.

#1) Power cord from wall to amp. this is where the most pwer is used and the most improvement gained from an aftermarket cord, in a general way. Most amps do better from wall than from conditioner. (I do use Furman Ref20i for amp... but I am crazy for clarity. It does inhibit LF a bit makes it all thinner...)
#2} power cord from conditioner to pre.

Agree with Elizabeth on 1. Then say 2., 3. And 4. A tie after that. I am a big believer in good power cords in proximity to gear and interconnects. I would upgrade my outlets before cords, YMMV.