ive heard that when u have dual voice coils u can reach different frequencies and get greater quality sound. ive also heard that if u connect ann amp to each coil it sounds deeper and better. be careful not too give each coil too much power though, itll blow the cone right out.on a dual it is also easier to manipulate the ohms by interchanging the positives and negatives
There is no difference in sound quality. The only difference is the wiring options that a dual voice coil gives you. As far as hooking them up to a single amp, it depends on both the impedance of the sub's voice coils, and the type of amplifier you have.