I am assuming your head unit has the 2-channel output for subwoofers if I understand you right. If this is true the all that you need is a splitter for your rca jacks to hook up the 4 channel amp. But the 4 channel amp can not be hooked up to one subwoofer. It has to be hooked up to 2, 3, 0r 4 subs. You can bridge the on side of the amp and use that for your dvc sub but DO NOT try to bridge one side of the amp and use it for one side of the DVC and then go and bridge the other side and hook it up the the other voice coil! Your subwoofer will be blown as soon as you turn the amp on.