Better question woudl be why would you use 1000 watts of power to achive 140db's when you could do 143 by using a second woofer and same amp.. Even if it can take 1000 thermally who's to say it needs that much mechanically? Power compression even as you approach most speakers RMS does become a factor. 1000 watts when you coil begins to get hot actually becomes 750 as impedence is rising.. 2 woofers and you'd at least be using your amp to it's fullest potential again lol. There are alot of ways to look at it, but IMO if you can put less stress on the speakers, gain overall output, gain effeciency and have the room and money it's a no brainer. Don't get caught up with "rms" it's a marketing trick.
On an extreme level, compare say steve meades van to Gmonks old one. Gmonk had like 16 12's or somethign stupid. He also had less power or nearly the same as Meade, IIRC. On a meter they were probably somewhat close. However, in real life, it's not. Meade was pushign his 4 18's HARD.. His woofers woudl smoke within a few minutes of use. Gmonks putting like 200 watts per woofer for the same output. No burning coils, no torn spiders. He also had that kind of acoustic effeciency over a much broader range. Term labs lie too, 160 from 25-90hz is ALOT different than 160 in a 3hz range.
