Don't take the def tech specs to seriously. Its not 14hz +/- 3dB. The mirage subwoofer IS 19hz +/-3dB though. I personally would go mirage. I've had a fair amount of time listening to the energy version (s12.3) and its a very nice subwoofer. Its fairly large, not SVS large, but big enough to produce low bass frequency's. On reviews its had an acclaimed in-room FR down to 15hz about 5dB's off its 100hz dB rating.
If you can audition both, do so. They both deserve a good listen.
SheepStar