680 is a little too rich for my blood. I've heard the 10" Ultimo. One of my co-workers had one. It was impressive. And it got loud. Don't let that "pure SQ" thing get you either. Little bastard got pretty loud too.
Until Morel get's a a better build house those things are't worth 1/2 that price. Honestly any SQ sub at that price range in a car is a bit absurd, unless it's also happens to get fairly loud ala an LMS ultra or something of that nature. Still a cool looking design though, like that you can see the coil, my sub uses a 6inch coil, but you can't see through the motor to look at it //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif
Ive heard them twice locally. I know the term SQ gets thrown around alot, but in the cases I heard them that was what there were in. Both systems were older guys that had really good home systems so they werent tuned to be loud. Both systems could get loud I guess, but that was the their goal. I guess there were tuned to be "Flat" as the subs werent louder than the highs. The subs souned more like music becasue they were just really fill on the low end. Again, like a really good home system sounds.