So I noticed that on your site the rms rating for the dual voice coil and single voice coil speaker is the same and so is the sensitivity rating. But when I look on crutchfield the dual voice coil design has a lower rms rating (270 watts) and a lower sensitivity rating (86). If this is true in theory then the dual voice coil sub can't get as loud as the single voice coil version because it handles 80 watts less and it is 5 db less efficient.
SVC rated at 350rms and sensitivity 91
DVC rated at 270rms and sensitivity 86