I just got a Big Belle myself. Just a FYI, I've been using one RCA plug for the sub channel input (mono sub output from headunit) and it works great. As far as I know, all the bridging module does is increase the signal voltage and give you phase adjustment.
Hmmmm. I was concerned about the voltage more than anything. My eclipse head has a phase shifter option. But the eclipse has 2 sub outs....do I just use one? I have to check if I have a mono/stereo option from the head.