I just bought and installed 2 of these the dual 4 ohm versions in nvx boxes built for the sub at approximately 1.5 cu. ft. each tuned to 34 Hz. I'm running somewhere in between 700-800 rms. They sound amazing. They are just as loud as my dual 12" kicker L5's in a ported box from 6 years ago but I don't "feel" it as much which is fine. They sound a hell of a lot better and balance out my 130ish watt rms front components and 100 watt rms rears.
At 2 for $199 (I got my pair for 169.99 on sale) I don't think they can be beat. Benefits are of course good performance in smaller enclosures.