You may wish to consider, for battery current efficiency, moving the battery from the rear of boat to a newly constructed or rear-extended engine enclosure to begin with.
Purchasing a six outlet DC fused panel such as: http://www.iboats.com/Marine-DC-Distribution-Circuit-Breaker-Panels/dm/cart_id.863290732--session_id.295013645--view_id.469687
Mounting all equipment on a single rack with room for more; running electronic equip NEG/POS cables of all elect units together through one appropriate sized sheathing, out the side to the rear of the DC fused Panel (waterproof)
NOte: Keep all negative leads the same length, this will prevent 'hum' on all boat audio devices. ; from the DC Fused Panel around the front near hinged end of top and up through an L type PVC fitting (mounted through front -- top of engine compartement) (preventing rain water and splash over from entering engine compartment).
Add total amperage usage of combined units and fuse inline at battery POS first, the amperage rating needed to power all.
Now you have switch controlled efficient DC Power that's fused both near the source (Panel) and the Power provider (Battery).