ditto on the above. On our current rig (Fleetwood Flair) I added a 750W inverter and ran a cord to an extra outlet I installed in the cabinet where the sat. receiver, DVD, TV plugs in. One thing I highly reccomend is to ditch the 12V batteries if you haven't already and replace them with 6v golf cart batteries. Much better amp hours in general and for running inverters. Also since we dry camp a lot I added 2 more for a total of 4 batteries.
When our new Georgetown 378 arrives near the end of the month I will do the same with it and also add a 230w solar system to the roof.
For a great site with lots of information about batteries, solar and inverters go to: http://bart.ccis.com/home/mnemeth/12volt/12volt.htm
This should be a must read for every RVr