The reason I ask is that by placing your subwoofers in opposing positions within the room, you are far more likely to acquire a flatter and more coherent frequency response through out the room.
Here is some reading material if you or anyone else wish to learn more about ideal subwoofer placement and the potential advantages of multiple subwoofers.
Harman International Subwoofer Placement White Paper
If this is all too much for you, jump to page 27-30 for a summary\conclusion!!!!
As the movie goes, your mojo was always inside you!!!!