Power handling is also limited by the wire itself used for the voice coil.
I'm not going to debate (sorry) as I'm no expert and this is not the thread to debate it in.(thread jack ). I know this has been discussed at the12volt.
In the end, I still suggest to the OP what I suggested. If he wants to get rid of his extra sub and buy a box to try a questionably sketchy setup... Be my guest, I wouldn't.