I'll put it to you this way, see how you wired your sub in parralel at the sub (pos from one vc to pos of other vc and same with the negative) what do you think would happen if you ran two more wires in parralel on the sub for neg and pos. Do you think you're sub would now be 0.5 ohms? Of course not, you're really just making the wire thicker by using two seperate wires, Well it works the same at the amp. If you have a final load of 1 ohm(for example) no matter how many wires you connect to the amp it will stay at 1 ohm cause that's the final impedance. Running more than one wire to the amp from one sub isn't the same as running more than one sub