If you want to tinker with your ship's power settings with different cores (including Fleet versions), engines, deflectors, shields, consoles, skills, etc., then download my Ship Power Calculator (linked in my signature). The Calc will show you what your power levels will be before you make any purchases.
You can find/contact me in game as @PatricianVetinari. Original Join Date: Feb 2010. Need Help with Ship's Power? Check out my Ship Power Guide and Calculator.