Any of the major manufacturers inverters would do for you.
Just remember the starting load could be triple (or higher)
than the running load.
The problem would seem to be with the battery bank. I would
not attempt to run a Fridge/freezer on 3 batteries. OK, maybe
3 forktruck batteries!!
You say that you have a 1500 watt inverter already and it will
run the entire load. But you are looking for recommendations for
an inverter?????
The only large inverters I have experience with is Xantrex. They
are great. My neighbor also has a Xantrex. I have heard many good
things about Outback. I'm sure others on here can recommend
several more brands. (As soon as the fever allows them to return
to normal. Was there a full moon that I missed???)
Here are a few sites to help you.
http://www.roadtripamerica.com/dashboarding/Power-Inverters.htm
http://www.crutchfieldadvisor.com/S-HqXVeUyLzvt/learningcenter/car/inverter.html
http://www.donrowe.com/inverters/inverter_faq.html
http://www.gsl.com.au/howto/howto_powerinverter.pdf
http://www.dcacpowerinverters.com/inverterguide.htm
They are not product recommendations, just an explanation of whether
you should get a modified or true sine wave. However they may have
links to try to sell you an inverter.
Ralph
"The best way to kill time is to work it to death!!"