well at .5 ohms, you figure the amp will do about 6500-7000 at 14.4v, so at about 13v+ itll do around 5500-6000. Just figure youre going to be doing 5500+ when the voltage is sitting at 13v, and you want it at about 14 im sure, so its going to be doing 2.5 to 3 times RMS then you were running before with the 2 dekas, so like I said you're going to need at least a couple more batts for sure, that's a lot of power to maintain, especially at .5.