I owned the Focal Twin 6BEs for about two years before I snagged the Sub6. I always knew the focals were good speakers, but something about them just didn't "click" with my head until I got the Sub6. It just rounds out their sound perfectly, makes you feel like you're completely immersed in the music. I've used bad subs before. They exaggerate the lows and make a room sound like your brother's souped-up car rig. The Sub6 has plenty of power (350W), but the bass it produces is incredibly clean, fast, and accurate.
So when you look at the spectrum analyzer and see always those very low frequencies right? With Focal Sub6 you can actually hear them and also see how the track will sound in the club on the big sound system, Well worth it.