I want to make up some alternate cables for my headphones how do I determine how many strands? would  silver plated copper wire give a different sound etc etc. I was just giong to use some decent speaker cable.

I don't know exactly what kind of headphones you want to recable but I would pay attention to the thickness, flexibility and durability of the cable. Especially portable headphones and IEMs need light and flexible cables. Too thick wire or wire with few strands is often annoying on headphones. Some thin, decent speaker cables can be surprisingly flexible and suitable for headphones.

Although headphones usually come with an "Y" cable, it's easier to use 4 wires if you use individual wires so you don't need to split the ground.

I wouldn't bother with any silver wire, just use your speaker cable or anything you like.

Anyway, recabling is pretty well covered on head-fi and there are many threads you can take a look at.