Where to put one's best power cords??

Depends on equipment and cords. No definite general answer. Listen. I would start by putting the cord on the preamp first, then move upstream step by step. After that to power conditioner if you use one and then to power amps. Unless specifically designed for digital, transports and dacs, good heavy gauge cord should work well everywhere. Purist Dominus cord that I have works best everywhere ! I left it on the integrated unless making recording from vinyl to tape - then I put it on the phono stage. I record directly from phono, no tape-outs.

How are we defining best or 'finest' in this case?

I have a Vitus integrated amp and separate CD player. The biggest effect was on the CD player.   A huge difference on some power cords (Shunyata especially).   On the amp the power cords had less effect, many had no effect at all. An improvement in the bass tautness was the main effect on the amp (again Shunyata was the most effective). 

What’s everyone’s experience with changing the power cord on a Node 2?