is your box ported? if it is then you dont want to use tones too much lower than that. If you're in a sealed box then you should be ok.
i would get the jl subwoofers or the mtx - but for an amp - if its not too late to change get an mtx - im tellin you - ive been throught the season of alpine - to jl - to mtx - - while ive never heard any complaints on kicker - ive never heard any re...
i dont like to buy used car audio for a very important reason. you never know how they used it. they could say ran for 20min @1/4 volume and it coulda really been used for a week overpowered and max volume. u could get lucky and get something treated...