AC lines

Is it ok to coil power cords? What is a good way to keep extra length looking tidy?
It would probably be better if you did not coil, but in stead just make one loop, like a long U. Make sure the legs of the U are not parrallel to speaker or line level cables.
I would run them back and fourth rather than coiling them. Coiling can create inductance in the lines. Also, as Njonker says, avoid putting them parrallel to the speaker or line level cables as your cables can then pick up RF from the power cable.
It is true that coiling a wire creates an inductor, but that is not always a bad thing. Inductors tend to block high frequencies, and if your power cord blocks high frequency RF from getting into your equipment that would be good.
I suggest you try it and see if it makes any difference in the sound. That's really the only thing that matters.