How short should a power cable be for my amp?

It does not make any difference on the length you decide on. Do you worry about the length of the cable from your breaker to the outlet? It's just a lengthening of that. If someone claims to hear a difference they are imagining it!

Thanks for your responses.It's that I'm trying to clean up the wires & the power cords of my amps, are to long.

it must reach recepticle with no stress to the wire from where it stands.

There was another forum topic posted on Audiogon where people were discussing the optimal length that a power cord should be to produce the best sound. Once again I'll stick with the first comment I made on this post. BTY; I have spoken with a few major power cord manufactures and they told me power cord lengths on the short side will not impair the sound.

Long enough to plug in. It's that simple.