Emergency Power to Weapons.
Engineering Bridge Officer Skill.
Even at Ensign level it's +14 (or more) to weapon power for the next 15 seconds.
You'll eat away at that first before dipping into the energy you set aside for weapons.
There's also an engineering console, Plasma Distribution Manifold. At later levels you can get +6 energy to weapon power. If that's where you want the power anyway, might as well give one a try.
I have 2 dual heavy cannons and 1 dual beam array on my escort, as well as forward quantums.
In the rear, I have 2 beam arrays and one quantum torpedo launcher.
I don't even need an EPS console because I don't fire every weapon at once.
Stagger your weapon fire. When one set finishes firing, use another weapon. This way you'll always do damage at a higher power level, which will make for more DPS, without that bottoming out of weapon power. It will dip, but not disappear.