House battery replacement

[wvphil]

Have a 2013 378 xl. Never been impressed with the house batteries as when leaving the frig on using only battery power the inverter has often shut the power off to the frig in around eight to ten hours due to low voltage if we are not plugged in to AC power. From what I've read on several blogs the batteries that come from forest river are not true deep cycle batteries but instead are similar to off the shelf batteries used for a trolling motor. Researching I've found that reserve capacity in the Trojan batteries ( I think are flood acid) have significantly more reserve capacity than the off the shelf trolling motor type batteries. They run around 200 to 300 each for the 12 volt ones I've seen on Internet. I've also read a lot of positive things about AGM type batteries being favored for their ability to maintain a flat constant output without voltage level dropping (which causes inverter to shut off to save batteries) down to around 20 percent charged. I've seen one AGM that sells for around 600 dollars that has around 260 to 280 ah reserve capacity which would provide significantly more reserve capacity then using even the Trojans which would be about the same price if I purchased two of them. However I'm reading it's important the AGMs are charged properly or the life will be shorter rather than longer then the standard type batteries. I'm wondering does the charger installed on the 378 have the capability to handle the AGM batteries and charge them properly? Does anyone have any advise (from experience not hypothesis) what batteries would provide better reserve capacity. I understand some of the newer 378's came standard with four house batteries but this is not the case for mine and I don't want to loose compartment space to go that route. Looking under the steps it appears there would be room to have a larger battery tray fabricated but not sure if enough room for a tray large enough for four house batteries. Additionally not excited about the possibility of someone burning my coach down or melting hydraulic lines while attempting this. Any (proven experienced) ideas out there?