Is nickel any good 4 speaker cable or power cords?

I have not yet read anything good about nickel being a good conductor. They main reason it is used is to prevent corrosion. "Buyer beware", if you decide to purchase a nickel product, I am sure every one would be curious to here what you think. You should look into companies that offer 30 trials, then you could test it on your system.

Nickel plating is used on copper conductors mostly for resistance to corrosion, resistance to high temperatures and to prevent copper from leaching through coatings of gold or silver. The price is lower conductivity (higher ohms/ft). Some high quality outlets and plugs, however, are nickel plated - so I can't see why nickel plated pc's would be a problem. But I can't see what benefits they would bring in a normal home environment either. As far as sonics, who knows - differences are heard in things when measurements or physical laws say otherwise.

Didn't the heating wires in toasters used to be cupronickel, an alloy of copper and nickel?

They might be good in colder climates.