If both of the subs are SVC(single voice coil), you could bridge the 2 channel into one of the subs(only if it is 4ohms). But you can't bridge a 4 channel amp down to one channel. So you could only us one bridged channel on the 4 channel amp. But, if the subs are dual 4 ohm vc, then hook one channel on the 2 channel amp up to each voice coil on one sub, and bridge the 4 channel down to 2 channels and hook it up the same way. Good luck.