We bought a generac 16,000 generator - plumbed with natural gas. The cost - about $5000 installed. Luckily we had easy location to a gas line (near our grill). It powers most of the important circuits in the house that are important (like refrigerators, stove, freezers, and of course the tanks) - and also starts automatically (which is important when one is on vacation, etc).
I would consider, though - considering the purchase of a battery which uses your home electricity to charge - then provides power when the power goes off - they can be pricey - but if I had it to do over again - thats the route I would go.
Wow, that seems like a REALLY good deal. I've always been under the impression that those generators were in the 15-20k range. I'm going to have to do some research now.