Importance of Power cords feeding Conditioners

I have heard it said that the most important power cord is the one into the distributor block. Well specifically I have heard it said at the Nordost roadshow demos, by the ever young and enthusiastic Lars.

At the recent UK show, he compared an all Red dawn cabled system, with an all Valhalla system. He changed one cable in the red dawn system, an Odin cable into the QB8 block on the red dawn system and sure enough, it sounded better than the all Valhalla system.

My question, if this is true and it seems so to my ears at the demo, that it is, is it equally true for all power conditioners? In particular, I am using a Pure Power APS 1050 regenerator. This is supposed to isolate the system from the mains by regenerating an AC wave form from a battery supply. In theory, this should make it immune to power cords feeding it. I will try some experiments myself, but has anyone got any comments about this? Thanks