Are manufacturer AC cables good enough?

Here in AZ, it's quite necessary to have a large home AC (air conditioning) unit. When my AC unit comes on, there is a momentary dimming of lights and even a slight flicker in the TV picture. The one thing, in which I detect no flicker of the lights, no glitch whatsoever in the sound or performance, is my audio system. I do have my system running through a moderately priced 15A APC power regulator/surge protector - mostly for surge protection, but I suspect that mostly the reason for my system's stable performance is do to the well designed power supplies in my components. JMO, if your very expensive amplifier requires a $3K aftermarket power cord to make it perform well, I'd trade that thing in for something that had a decent power supply and performed as intended out of the box, with the cord that was supplied....Jim