i have 1 x 12" Kicker "comp" sub in a pre-made box and it kicks damn hard, currently running it off two channels of an MTX 4 channel amp with the other two channels running Kicker splits up front but i may end up using my other alpine 4 channel ( mrp250 i think it is ) and have it dedicated to the sub though

therefore, id got with what IMPRESIV said and get a good Kicker sub in a pre-fab'd box, mine cost $250 from AudioCom Bunbury a couple of years ago and i havent looked back. makes all the noise i need for not much $$