if you are getting two subs get the D4, if you are getting 1, get a D2. Trust me, i made a mistake and i am still regretting it. i got two D2 subs and now i cant run @ 1ohm unless i buy two seperate amps. .5 ohms will risk your equipment and two find a amp that gives out the kind of power you need @ 2 ohms will be expensive.