Pat, those Raymarine units do suck a lot of power... I have a good set on my 30 Grady and have set up the batteries in a way to maximize the available power to the house bank. I can't tell what boat you're running or how many batteries you have, but here's some tips I found helpful:
1- as mentioned, look for high amp hour batteries for house needs.
2- I have used voltage sensitive relays between starter and house, to keep my starting batteries isolated so they don't drain from my use of electronics, but the starter battery charging can add power to the house when in use. (I have a GRP 24 starting battery for each of my two engines, and two GRP 27 linked together as one battery for house... each start battery is connected to the house bank via VSR to isolate, yet charge house if voltage of either start bank goes above about 13V I can't remember the exact number...) I swap engines every two hours trolling, and it seems my alternators do a good job of keeping starters charged and power flowing to the house bank.
3- A little DC circuit breaker management while you're underway to assure your house isn't unnecessarily powering something you don't need. Washdown pumps, fridge, etc...
4- LED lights