be carefull with the fly trap amps. they seem to overheat all the time and melt the wires inside. im asuming its the one in the bazzuca box? grey felt cover? plastic cone?
the plastic cone will allow yo hard thmping bass, but what i would advise now would be to go out and buy a really soft, 8" sub. this will reflex massivly, and give the grumble, and people outside your car would hear it from miles away

with quality bass rather than thumping load bass
you would require a new amp as the fly subb you have has a built in amp. but that aint a problem. 2 amos arent a bad thing. normally i would run two subs off one power amp whiwh has a strong two outputs. this way you dont kneed the two amps
dont rush into buying amps..or subbs.. there was plenty of better deals i could of found for you, instead of the trap subb and amp you have now.
also, does your head unit have a sub-out???????