So my subwoofer (Alpine Type R 12") is dual voice coil 4 ohm. Now what I'm confused with is it's wiring down to 2 ohms (for 500 watts RMS). I wired down to "2 ohms", but is that per voice coil, making it 4 ohms, thus leaving me with only 300 watts RMS? If so, does that mean I'd have to wire it...