Actually they are good subs (made by JL Audio) i have had experice with the Ultra drivers, Solo Bass, And Pro Bass series (replaced by the beasts)
This was back in the days...
The ultra drives (2 10's) slammed for a smaller sub. The problem with them were that the copper wired that extend from the terminals to the spider would keep breaking on me??? It was a pain and after the 3rd or fourth time they broke i tossed them.
The solo Bass's were o.k. They sounded nice but the power handling ****** on them. But i just got those cause at the time i didnt have room for the enclosure.
Now the Pro Bass's were some bad ass subs. I ran them(2 12's)off 2 soundstream MC500s (gawd i miss them amps //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif ) and they hit hard as hell. I had them in the back of a little CRX and they would rob your breathe from you. The downfall was they were hard to push, and they were not designed for the smallest of enclosures.
So i guess the quality all really depends on what series you get. The amps are nice, but i would go with a amp other then Cadence to drive the subs, you can find more powerfull, cleaner, and cheaper out there. But if you do go with a cadence amp that **** thing will last you forever. Later