Find an amplifier voltage output to match my subwoofer rating
OK, so it's car audio.
Each of these woofers has 2 liters displacement volume at xmax, so +/- 1 liter, if we assume about 2 cubic meters volume in the car, that's a neat 1 liter per cubic meter, so an overpressure of 0.1% of sea level atmospheric pressure, or 100 Pascals, or 100 N/m². So, your windshield should not explode, although everything that is not bolted down (with loctite) will rattle. But, well, it's still 134dB acoustic, so the amount of time it takes to go deaf depends on frequency. Make sure you put on your earmuffs for testing.
Now &quot;RMS power&quot; doesn't mean anything. &quot;RMS volts&quot; does, it's the Root of Mean of Square of instantaneous voltage, which is used to calculate power in a resistive load. But it makes no sense to take the Root of Mean of Square of a power. What it usually means in audio lingo is how much average actual power it can output (or take if it's a speaker) for a reasonable amount of time without being destroyed. It's a way to distinguish the numbers from all the other fantasy sales brochure watts like musical, PMPO, etc.
Before believing such a power rating, I would like to see more details, for example for an amp &quot;750W for 60 minutes in resistive load&quot;, or a mention of how long it takes for the thermal protection to trip, or something like that. Without these details the numbers should be taken with a grain of salt.
If these manufacturers can be trusted, then the speakers won't burn out. Note you can still destroy a woofer without exceeding its rated watts if you use an enclosure that allows it to exceed xmax and bottom out. Sealed enclosures are usually okay because the pressure inside prevents the speaker cone from going too far, but this is not the case with bass reflex or any enclosure with a vent. So you should be careful about that. Unless you're deaf, you will never burn the woofer with watts in a car, because that's way too loud and it takes a while to heat up, so you will turn it down before it fries. But if it bottoms out, it can be destroyed very quickly. So it's a good idea to do a frequency sweep at low power and find the frequency that results in maximum cone movement, then from that calculate the maximum signal level that you will allow, and set the limiter accordingly.
Note if there is a hole on the back of the speaker magnet, this is for cooling, so don't mount it against something that prevents it from sucking and blowing air in and out to cool the voice coil as the speaker moves. This also means there is no cooling at DC, so if the amp dies and outputs DC, the speakers will fry.
2x750W will require 125 Amps from 12V (assuming 100% efficiency) so the limiting factor will probably be the car's battery or alternator.