How can power cords make a difference?

They can't. They don't. Never will. Nope. No way, no how. Don't even go there. Not another wasted moment of your valuable time should be spent on this silly, putrid, over-hashed, science vs. religion, bulemicized weekly, electro-acid refluxed topic. Snake oil, nothing, we're talkin' snake bile here, folks. Don't bother, I'm telling you.

Or...if'n years of schooling don't prohibit you from exploration, you could try it out for yourself, and then choose your rebuttal weapon accordingly. Rest assured that once you've completed your listening test, not only will another thread appear with the identical question, it too will end up in the same place as all those preceding it.

Ssshhhh, don't tell anyone, but you're absolutely right . . . it is voodoo.

Edkoz, you should look into the archives as this thing has been covered ad naseum.
I completely agree with you regarding cords (congrats on not calling them chords), and you'll often see the most adament arguers are also those that insist double blind testing isn't necessary, as the "know what they hear".
If you've got EMI and RFI covered, you're good-to-go. Don't buy into the power cord silliness.