I've owned most of the cords listed here so far, and lived with them on my EC 1UP. Also used Synergistic Designers Reference Squared (a mammoth power cord and their top of the line). But the one I have settled on is the Electroglide Mini Kahn Plus.
My second choice would probably be the Harmonix Studio Master, but it's not as good as the Mini Kahn on digital source. Loads of air, detail, and shimmer. Great bass control, and smooth mids. The most analog (to coin an over used term) sounding of them all.
Good luck!