...power cables can only be as good as the in-home wiring coming to the wall socket.
This is not entirely correct. The main culprits negatively affecting your hi-fi gear are devices plugged in in close proximity, so the power supply of your CD player is affecting your amplifier ( and vice versa) more than your kitchen appliance that may sit on a different circuit. The more hi-fi gear you have plugged in the same or near socket, the more cross contamination you get. And all your hi-fi gear is closely interconnected through, you guessed it, the power cables.
The upgraded wiring/dedicated high quality circuit is of course a big improvement in most cases, but it depends on the quality of existing wiring/supply.