What speaker gauge for my setup?

[Glen B]

Right now I am using pedstrian 18 gauge speaker wire with my Behringer EP2500 that outputs 450 watts RMS 20hz to 20khz into 8ohms. My speakers are slightly modified DCM KX12 Series 2 speakers with Pioneer 4ohm car subwoofers replacing the original woofers. Funny the original woofers were also 4ohms even though the nominal impedance rating is marketed as 8ohms. I think it is really closer to 6 but anyway I'm wondering if an investment in 14 gauge or 12 gauge speaker wire is worth it. The left speaker is using only about 3 feet of wire and the right is using about 7 or 8 feet. I can't believe that 18 gauge even works at all for this app but I guess the distance is so short. It sounds good but I would like to know if getting new wire is more than likely going to make a difference or for this distance am I okay? It seems to sound a bit harsh. I had 12 gauge speaker wire attached a long time ago but I don't remember what it sounded like and I must have tossed the wire in the trash because I can't find it.

I checked Wiki but I don't think they mention the wattage factor if there even is one.

I will differ somewhat with most opinions here and suggest that for your short distances, 16 gauge wire would not be inappropriate, especially with a non-revealing system. The resistance of 8 feet of 16 gauge wire is approximately 0.03 ohm, well below what it would take to cause frequency response problems in the fussiest of high end speakers. That said, wire is so cheap, it does not hurt to use larger gauge wire, like 14 or 12 gauge. There are those who may disagree, and that's their prerogative. I've been in this hobby more than four decades, 11 of them in the past in the DJ/sound reinforcement business, so I've been "around the block" more than a few times. You also mentioned system harshness. Larger wires will not solve that problem. Try better quality speakers and better source equipment.