If I can afford one good cable, which component?

In my experience, putting the best power cord on preamp or integrated is the way to go. Not on the source, not on the power amp. And the rest of the cables, yeah, follow the signal. However, as Elizabeth said, it might be different in different set-ups even if only to a certain degree. Current from the wall and regenerators/conditioners is another subject.

I'll give you two American cents for your couple of euros. Do we have a deal?

Euro will survive, no worries. As for "rubbing sticks together for fire", that's exactly what I wanted to do a month ago when the power over here was cut for a few days and it really got cold in the apartment.

If not overtaken by yuan, dollar will be forever. Dollar and Swiss franc.
Anyway, let's put good American made power cords everywhere and enjoy the music, mostly not American made. At least not for me.