My only regret about snake oil is that I'm too honest to make money
out of it too...

For a short run of a few metres, just about any cable will work.
Getting one of the right impedance would be best, to stop reflections,
but SPPDIF is hardly the world's best designed electrical interface.
The connectors really are so bad that you need not worry about them.

Silver plating is a waste of time. The resistivity difference is so
small it's not going to make a blind bit of difference on a digital
signal. The SPDIF receiver won't even notice 6dB of loss.

The full bandwidth of the SPDIF signal is tens of MHz if you want nice
sharp edges. If the edges are sharper then there's more change of
getting good timing back out of the signal. It might be digital, but
the timing of the 0's and 1's will affect the final audio quality.

The biggest variable in all of this is the SPDIF receiver chip. There
are many crap ones out there. I know. I've used them. They don't
recover good timing information and so the resultant sound produced
gets degraded. I also work in the design team of a chip company that
doesn't produce a crap one...

So for ultimate audio quality, use a one-box player to avoid the SPDIF
link if you can; or find a system with a properly designed SPDIF...