Looking for a musical subwoofer @ $500>

Had some thoughts, but figured I would ask here as I was given some great advice for my previous amp/preamp questions: https://forum.audiogon.com/discussions/amp-preamp-or-avr-for-home-stereo-and-entertainment

System sounds great btw! Parasound A23, Integra 80.3, KEF Carina II's, Technics turn table, and a Blu Ray Player. 

Anyhoo - I could use some more bass. The KEFs get down to 55hz but a lot of my music goes lower and I don't want to compromise... to a point. 

Looking for a sub capable up 25-30hz on the low end with anywhere from 8-12" driver for less that $500. I came across the Klipsch R-12SW and the reviews were stellar, especially for the price. Want this for music more than Home Theater, but both would be nice. I've even read that the Pioneer SW-8 or 10 is a fine unit for the price. 
I know of names like Sunfire and Velodyne, but I wonder if it's worth buying into those companies if I can only afford the lower end products.

Also, my guess is that buying a used subwoofer is like buying a used race car... expect it to be driven, hard. 

Thanks in advance!