how can i get the 1500w at 14.4 VDC ?

 

if you hook it up right you will get the most power you possibbly can. to get a full 14.4V you will need an upgraded alt and some 0 gauge wire even then when the bass hits it will drop below 14.4. !14.4 is only possible if it was a perfect world situaltion. I was just using the 12V rating since most of the amps i use give that as a rating. My friend had that amp i thought it was 1000x1@12V maynbe it is 1200

Bottom line don't worry about the numbers hook it up in parallel and you will be getting the most power possibleout of that amp.