Paradigm PDR series are Paradigm's lowest end subwoofer offerings, but that doesn't mean they are bad. The PDR series has been offered for over 10 years, and all the while they release new versions of these subwoofers once every 2-3 years. It would have been wise to buy this subwoofer on resale value alone, the cabinet would be worth $50 to someone, if the whole subwoofer works, it's worth a lot more than that. ($150-250 respectively).
And yes, it's a better subwoofer than the Polk. I had a PDR-8 that was better than most Polk subwoofers, I liked that little subwoofer, I imagine the PDR-12 is pretty good.