Can you bridge two sub woofers with one system?

Yes. If you have two subs you can connect them to a single receiver via an RCA "Y" splitter at the LFE output. This will allow you to run two subs out of one receiver. You'll need to make sure you only calibrate one at a time and realize that having two in the same room will give you a 3dB increase in volume over a single sub. The best place to put dual subs is either in the center of opposing walls (against the walls) or in opposite corners.