Buy a power cable that is rated higher than your maximum required volts.
Thick cable = better. Lower AWG and monoprice makes some nice power cables.
So long as the tolerances of electron flow are not surpassed, you have a perfect power cable. So for example...if you had a really thin and cheap power cord and plugged In power amp with it, the cord itself would probably catch on fire.
I like 14 AWG or 12 AWG power cables. Above that is really not worth it.
Shorter power cables are also better. Lower resistance and slightly better performance.