Let's see your electrical current travels X number of hundreds of miles from the generating plant and you are asking if a thicker cord will make a difference the last 4 to 6 feet????No it doesn't.
09-24-10: Vernneal
No actually it is an extension of the primary winding leads of the power transformer.
Depending on the make-up of the power cord it can do more than just deliver AC power to equipment. It can also filter EMI/RFI from not only entering a piece of equipment but also from exiting and getting back on the mains and contaminating other equipment. Example EMI/RFI hash from a CDP going back out on the PC on the mains only to re-enter a preamp or amp. Switching power supplies are notorious for putting hash back out on the mains.
Another thing a power cord can do is prevent EMI/RFI from transferring to ICs near the power cord.
And lets not forget the electrical connectors used, the plug and the IEC connector. They alone can make a difference on the delivery of the power.
And one other thing the utility transformer that feeds your home and maybe four other homes is a step down isolation transformer Two separate windings....
Most of the EMI/RFI, and harmonics that affect our audio equipment is created right there in our homes,.... though the power company gets blamed for it. One of the worst devices is that computer you are using....