I recommend starting with a Power Cord if you are going to upgrade entire cable loom. And if you aiming at “Million” series IC and Speaker Cables down the road then I would start off with 聖Hijiri SM2R-L "SOUND MATTER" Power Cord not Nagomi. The SM2R-L performance is closer to “Takumi” Maestro PC and offers amazing synergy with “Million” IC and Speaker cables. Nagomi PC is good but SM2R-L PC is simply on another level.
If I were to start over and on a budget, I would buy one “Takumi” PC for Integrated or Amp and SM2R-L PC for rest of the components.
Hooe this helps!