If firing arc is your concern, there are single cannons as well. They have slightly less damage then dual beams but an even wider arc ( if I remembet correctly) and they go better with your other cannon skills and consoles.
Dual Heavy Cannon - 45 degree arc
Single Heavy Cannon - 90 degree arc
Single Cannon - 180 degree arc (just like beams)
The SC lets you use your Cannon skills and still have beam coverage. Does slightly more damage than beams too.