all subwoofer performs with door close....
are u gonna drive your car wif your boot open?
u gonna need huge ported subwoofer enclosure to "amplify" the sound.
u do need a high power monoblock to power up a sub, if u prefer your car as a mobile disco. ;)
box determine how the subwoofer sounds like.
this is a budget sub, and one sub won't help much. u probably need at least two sub. or maybe four.