Would you fill in some of the details of what you know about power cords? You've told us that a power cord that's not up to the job is going to hurt the sound, but what are the basic requirements for an adequate power cord? One that will not degrade the sound in a system the average 'Goner might own.As a general rule of thumb I go with heat. If the cord makes any heat at all, in the middle or on either end after several hours of operation, then its not up to the task of working with the component its powering. At that point a heavier power cord can be very nice. The connections on either end can be important- if they heat up it won't matter much about how good the cord itself is as the voltage drops on the connectors (hence the heat) will overpower that.
I have a cheap solid state amp in my bedroom system that makes about 5 watts per channel on a good day. It does not need much of a power cord. But with a 60watt tube amp you can notice differences (and measure differences too) quite easily. So there is a scale issue here due to Ohm's Law; consequently what will work varies from product to product.