Best place in the system for a good PC?

I decided to develop my own opinion as to whether expensive power cables help or not and purchased one. For those of you who feel they improve soundstage, attaching the good cord to which component gives the largest change?

If you don't believe PC improvement, please reply to the post below this one entitled "Power Cables which take the soundstage back". I'm not trying to begin a debate; I want to see it for myself before I chime in.

Thanks All.