I have asked the folks at SV Subwoofers a similar question. I asked about using two different subs of the same size and basic configuration (both 16-46 models, but with different amps, and drivers) their recommendation was not to mix subs, even units as similar as these. There concern was that it would be difficult to balance the outputs of the two dissimilar units. Since subwoofers are their business I have chosen to heed their recommendation. In short sell the sub you have, and buy two of the ones you want. Don’t mix.