upgrading to an adequate guageThe cords that came with your equipment are of adequate gauge.The mfgr. would not include a cord that couldn't handle the current required for the equipment.There are codes and regulations that govern this.
having them in the correct lengthsYou can easily make your stock cables any length you want.
Have any of you used these diffent PCs and can you comment on their sound?I have to agree with Tvad that at this price range you will not hear much,if any,difference in sound quality.
When I bought my equipment(used) the stock pc's were a little loose so I bought 2 PS Audio Power Punch cables to replace them(PS Audio has replaced the PP with the Jewel,BTW).I was not expecting nor did I hear a difference in the sound but the connectors sure fit good and tight, which is what I wanted.Remember,these are just my opinions,humble as they may be.Good luck in your endeavors.