A while ago I purchased a set of Z506 Logitech speakers for my living room HTPC on sale. Until today, the rear speakers were just sitting on top of my entertainment center. I finally got off by butt and ran some 18 Guage speaker wire from one wall to the other (I have an open basement which made this quite easy) and now I can plug the rear speakers into the wall in the back of the room.
There was really no trick to extending the speakers, I did some research and seemed to find that 18 guage wire was the most common to extend RCA type speaker plugs. I then ran 2 lines of the wire and finished it off with some RCA keystone wall plugs on both walls. No ugly wires across the room, and surround sound to boot!