When you consider electrical conductors (as in AC power cables), the ability to pass lots of current is directly related to the diameter(cross-section). If you need to be able to pass lots of current, you need fat conductors. But if the voltage can be increased, you don't need to pass so much current (again for the same amount of power), and you therefore don't need such fat cables.
This means that the power-handling capability of the same power cable will be increased by running it at 220~240V AC, as compared to 100~117V AC. The same applies inside the power amp (for the power supply input wiring and circuitry up to the power transformer). By running it at 220~240V AC, it is effectively "getting an upgrade."
The limitation on voltage handling of electrical conductors concerns physical spacing and insulator material (and thickness). Usually, the wiring inside a modern power cable (and also the power supply input wiring and circuitry up to the power transformer inside a modern audio component) should be able to handle 240VAC without difficulty.