Hi,
I replaced the original house battery on our Bavaria 36 with two 150Ahr AGM batteries. I also fitted a Balmar smart regulator and a Xantrex battery monitor. This set up seems to delivered a sound balanced charging system. Oh, replacing the lights with LED is also a must.
My next move will be to tackle the fridge, which seems to run more than I think it should. I believe the most effective improvement is to work on improving the efficiency of the condenser by increasing the draught of cool air throughout the fins.