I'm sorry guys but all these suggestions are going past what I would say "The BEST PLAN".
Build a 2 inch thick MDF box go and get yourself a "Nice"little generator(GAS),Tuck it away and keep the Voltage up.......
It is a hell of alot easier to fill a gas tank every 6 hours then to charge every 2.

 

I have 5000 watt gas generator already vented below deck.How do I run that to system?Do I just get 1 yellow top and run charger to it as system is playing?

 

If you have a generator already just get a 60-100Amp 12volt power supply and plug it in to the generator. For the price of one or two yellow tops you can have a nice 12volt PS and then no worrying about batterys.

 

sorry,not sure what 60-100 amp 12 volt power supply is?Is there anywhere on internet I can look at them?

 

What I'm trying to say is how do I get 110 volt generator down to 12 volt nicely?

 

Sure right here.

http://www.nipponamerica.com/catalogue/jpg_NA-302.htm

 

The bottom 1 looks good but can't click on it and see any prices.Is something like that really expensive?

 

Cascade Audio makes some great power supplies for this application, IIRC, I just had a e-mail with some sale pricing on them as well.
http://www.cascadeaudio.com/aps.html