I just bought a 2001 Jayco Eagle class C and am upgrading before going south. I'm adding two 125 AH AGM batteries and a 1000 watt inverter and have a question about batteries. Will it be bad to parallel the AGM's with the old lead/acid house battery? I've heard something, in the past, about it being bad to do this. Should I just throw the old battery away and use the AGM's?