If I were to use 4 subwoofers, I would need to custom stall wires and run them about 20 feet to the back wall..
I researched subwoofers for a year and I thought REL's were the way to go. Their high level connection allows them to act more like woofers than subwoofers. You can adjust the gain, volume and crossover. I am playing my two S2 SHOs at 40% volume. I also feel two subs are far better than one for room balance. My secon choice was Rythmik F12SE.
Carbon Miller knows the most about running a 4 subwoofer cluster. This makes sense because it fills the room. If you have any questions about how to use subwoofers in your system he is the most knowledgeable. Averall, he is one of the most knowledgeable in our discussion group. He is also one of the most willing to help.