Projector Power Cords

I have seen significant improvements in video quality when upgrading the power cords directly connecting to the display device.  The last 3-6 feet of conductors in the power line are the most important.  I've also seen big improvements when using linear power supplies on any equipment feeding the video signal (such as video processors / switchers, source devices, HT processors, etc.).

Copper will have a warmer/slower result in both audio and video if you use typical gold-plated plugs.  Silver, of course, is much faster, but also has its own problems.  I've found the absolute best is solid-core pure copper with rhodium plated connectors.