This thread has been idle for a while, and I'm generally more of a researcher rather than a contributor. Assess that as you will.
I've always been an advocate for good interconnects and speaker cabling, though I don't spend 1000s. I like DH Labs for interconnects and have used a few different speaker cable brands over the years.
I'd never felt the need to invest in power cabling, but can honestly say after doing so recently, it makes a significant difference for me. Nothing fancy here, just Pangea AC14SEs and a couple of AC9s bought second hand.
I have a few different system setups I play with here; NAD M3, Schiit Aegir as monoblocks with a Freya+ pre, Audiolab 6000a, Denafrips Pontus, Focal Aria 906s, VMPS RM30Ms, Zu Omens, Von Schweikert VR4s. With all of this equipment, the power cables made a difference. Move me to the believer column, thanks.