I built a four outlet box for my p300 using a short 18 inch 12 gauge power cord and soldered all the internal connections. It works very well, no difference in sound compared to plugged directly into the p300 outlet. All you need is available from a hardware store.
Extension Cord
I bet you thought some idiot wanted advise on using an extention cord on their HI-FI system. Actually, I would like to know if you could use a good heavy duty, three prong extension cord going to a PS Audio power plant since the wire running to the outlet is probably no better.