Okay, Tom Nousaine's Lab measurement (<10% distortion, 2 meter distance, 7,500 C.F. room):
SVS SB12-Plus - 32-62Hz Average = 104dB; FR = 34-116Hz +/-2dB; Bass Limit = 32Hz @ 102dB.
SuperCube I - 25-62Hz Average = 103dB; FR = 30-120Hz +/-2dB; Bass Limit = 25 Hz @ 78dB.
So my interpretation is that the DefTech SC-I goes lower than the SVS SB12-Plus!
So I would buy the SuperCube I.
http://home.comcast.net/~frank_carter/Nousaine.htm