inverter advice

Sounds like we have the same inverter set up , my 400 watt unit had been replaced by a previous owner with a xantrex SW 600. It's been working great for the 5+ years I've used the coach. Looks like the replacement would have taken a half hour at most. It's all the inverted power I need, right now. No charge function required.
If I install a residential fridge , I would up grade.