I have the APC H15 and the power cord is one of the most substantial I have seen (bigger than my power amp). APC quote 12 Amp rating because they are extremely conservative.
Frankly I can't see how a power cord can make a difference to any gear ( unless it has ACTIVE components inside that filter something ) Your APC S15 already has some inductors to clean up high frequency noise and to isolate each outlet device - this set of ACTIVE components in your APC is hundreds of times more important than any PASSIVE piece of wire (no matter how beautiful and "expensive" the esoteric power cord, it is essentially just a piece of wire like what you have around your house. (Caveat: some tightly "woven" power cord designs may actually have some mild inductive filtering properties for high frequencies, as an inductor is made from many loops of wire)
Furthermore, APC test their gear with high powered amplifiers so you can be assured that it won't limit current flow to the amp. Adding further filtering on top of the APC circuitry is ill advised IMHO (ultimaetly if you keep adding filters then you WILL restrict power to downstream devices).
BTW: I'm a tin-eared engineer so I am probably not to be trusted (being highly skeptical of any tweak that has no plausable physical or scientific explanation...)
Frankly I can't see how a power cord can make a difference to any gear ( unless it has ACTIVE components inside that filter something ) Your APC S15 already has some inductors to clean up high frequency noise and to isolate each outlet device - this set of ACTIVE components in your APC is hundreds of times more important than any PASSIVE piece of wire (no matter how beautiful and "expensive" the esoteric power cord, it is essentially just a piece of wire like what you have around your house. (Caveat: some tightly "woven" power cord designs may actually have some mild inductive filtering properties for high frequencies, as an inductor is made from many loops of wire)
Furthermore, APC test their gear with high powered amplifiers so you can be assured that it won't limit current flow to the amp. Adding further filtering on top of the APC circuitry is ill advised IMHO (ultimaetly if you keep adding filters then you WILL restrict power to downstream devices).
BTW: I'm a tin-eared engineer so I am probably not to be trusted (being highly skeptical of any tweak that has no plausable physical or scientific explanation...)