I just added a second 1X12″ 120W subwoofer to The Home Theater From Hell.
Why? One word. Headroom.
Modern soundtracks make pretty heavy demands on home theater sound systems. If you have a crappy little soundbar, that’s going to get overloaded and possibly even push the amplifier into clipping (distortion) during the peaks that abound in today’s movie soundtracks. (movie soundtracks? these days even COMMERCIALS have low-end artifacts that sound like a tank coming down your street)
Nothing sounds worse than a speaker / amplifier system approaching its limit. Amplifier manufacturers even put compressors in the amplifiers to push back the wattage when peaks hit so the amps don’t crap out.
Look at it like this – you have two cars going 80mph. A Ferrari and a Volkswagen.
Suddenly, you need to be going 90mph. The Volkswagen might do it, but the motor is stressed to the breaking point.
The Ferrari? Effortless acceleration.
The amount or reserve power in any speaker system isn’t about volume. It’s about CLEAN volume.
The speaker size / capacity also isn’t about volume. It’s about barely pushing the speakers to produce that volume. I use JBL 4412 studio monitors for mains, which also have 12s.
This is why I have double the wattage and speaker capacity most people would consider adequate.
That’s also the reason my bass rig sounds so kick-ass. (IMHO)