ohm rating has nothing to do with better bass, it's all about wiring. With dual 2 ohm you can achieve a 1 ohm load or a 4 ohm load. with dual 4 ohm you can achieve a 2 ohm load or an 8 ohm load. Most amps will put out more power at a lower ohm load giving you more power to your sub, but your amp has to be stable down to low ohms. So if your amp is 1 or 2 ohm mono stable buy the sub with dual 2 ohm coils, even if it's not then buy the sub with dual 2 ohm coils so you can wire it to 4 ohms. To wire it to 1 ohm wire it in paralell, to get it to 4 ohms wire it in series paralell. ask others for wiring diagrams.