I have a RCA RTD315W hone theater system, it's been working great except he speaker wires are too short. I have to place them on tv trays when I use the system. I would like to mount the speakers on my wall, so how do I find out what size speaker wires to buy and whagt are the steps to lenghting the wires?

You cast your Mark I Eyeball on the speaker wires then buy something like it at Home Depot. Lamp cord will probably suffice and it's cheap. Buy a spool of it. Then you TURN THE UNIT OFF and carefully splice in the desired length of wire (*), one conductor at a time so you don't criss-cross anything. Make sure you leave NO conductors exposed in the joints.

* They make a number of solderless splicing devices. Ask the guys at HD when you buy the wire.