Generac sells a natural gas fed generator that will run the whole house. You're looking at a $12k to $15k investment. My buddy owns one and it kicked on 30 seconds after he lost power.

http://www.generac.com/Default.aspx

You can go for a cheaper diesel model, but you would have to be concerned with fuel storage...especially for 8 days worth of continuous service.

I feel your pain. We just went thru Gustav and were without power for 4 days.