SIKCVC is completely correct here. The sound would be absolutely turd. Not only some cancellation of waves might occur, as suggested , drivers play different frequencies better, irrelevant of the size being exact. My honest opinion is to get 1 good sub. In any Honda it is more than adequate. I have a Boston Pro 12" Ready to go into my tegs, giving it 500 rms, im sure it will be enough! (cant wait to hear it!). As for the amps, its generally better to have the same amps powering the usbs (if using 2 sub amps) unless you have access to a digital oscilloscope to ensure you are giving each sub the exact same power.