Says right here on the company web page "Discontinued":
Ultimate, Uncompromising Bass. 15” Driver with Patented ART™ Surround, App Control, High-Velocity Low-Turbulence Ported Design, Anthem Room Correction (ARC®) Included.
www.paradigm.com
Like I said, you may find old stock still available, but it is out of production.
Recommendations above are good. JTR has high output so a good option performance wise. I would lean towards Hsu or SVS myself. I can't get Hsu in Canada so went with SVS for my system. If you're in the U.S., Hsu make great performing subs with beautiful cabinets at a competitive price. SVS has been making good subs for years but prices have been creeping up. They do include a nice app for setup and have the widest range of options available.