Can POWER CORDS really make that big a difference?

Sure. I found that some had a noticeable effect and others appeared to have no effect from stock cords. I also noticed that the effect was similar with amp, preamp and cd player with each cord. Each apparently has a sonic signature. Silly but it does work most of the time.

I would spend the money on power devices that will make a difference such as PS Audio power regenerators, etc. Other than that have all the light dimmers revomed in your house. If you can not have your neighbors to agree to do the same, then have your power company run a direct line to your house from your substation. There, you will hear the difference.. of course, IMHO.

In a word, yes.

Yes, but not always for the better. As others have suggested, i would "try before buying" i.e. pick some up from a dealer or company that allows returns if you don't like the results. Some cords seem to have very strong sonic signatures whereas others aren't nearly as evident. Sean
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Yes. I made some from Belden 83802 and good connectors, along with dedicated lines from same. The dedicated separate lines for the CDP and the pre were more important than the PCs, I think. Have fun, but DON'T spend big money here....