What gauge speaker wire is best to extend my home stereo speakers?

I live in an upper level apartment. We were recently given a very nice entertainment center that some former renters had left behind. The only place my home stereo fits is on a shelf on the bottom of the E.C. resulting in the poor placement of it's speakers being too close to the ground. As they sit I can't listen to it at a decent level without getting complaints from down below. I need to add some speaker wire so I can place the speakers in a better location. So I went shopping for what I thought was a simple roll of speaker wire and was faced with many different gauges of the stuff. Which gauge would be best to use. Also, will extending the wire effect the sound quality. I think I may need roughly 3-4 feet per speaker. Thanks