EDIT: Also, would I still be sending 750 watts of continuous power regardless of gain and volume? How does that work?
Edited by JJJMan75 - 6/3/14 at 8:28am
Power in this case is a function of the voltage output of the amp and the resistance of the speaker.
The speaker is probably somewhat linear in resistance so that leaves the voltage of the amp to control the power.
If there is a gain switch or volume knob then this controls the voltage and this power to the speakers.
Keep the volume down and the power ( Watts ) goes down with it. You should be fine. Just use your ears and best judgement for the volume and the setup should work.
Like headphones is is more about the actual performance and scientifically acquired data rather than simple sales specs. A higher rated sub may be able to handle more power from an amp, but you really will not know exactly how much the sub can take without having some serious science behind the numbers. That or just listening to it while it is being driven.
Higher quality subs will be made from better materials and have better designs leading them to have better sound. This means clearer sound, lower likelihood of distortion, and can handle higher volumes.
As for your volume / power question this is where sensitivity comes into play. Depending on how the speakers is designed such as how many wraps of wire make up the coil along with other factors make up how much power is required to achieve a volume. One could have an easy to drive cheap sub and a hard to drive expensive sub.