You will get different opinions from different places, but on this website people pretty much deal with numbers, and the numbers indicate that you already overpaid on your speaker wire, and spending more is up to you.
Good wire is good wire and as long as it carries the current as expected, you will hear the audio as intended. Copper 12-14 gauge wire, available at
www.monoprice.com is ideal for pretty much any consumer grade speaker in the world.
Save your money. If you think you will get an improvement with something else, first try something really inexpensive and try for a blind test of the wires you already have and cheap wires to see if you even can tell a difference.