fast bloke

as you guys seem to know everything...[brownnose brownnose], I need to run a TV, a dvd player and a laptop powered from motor home alternator/battery (12v) when it is on the move. Someone suggested a rectifier, which will give me a 230ish volts AC supply from a 12v DC supply, but my memory of physics all those years ago tells me that this will leave me with a very very small number of available amps. Can anyone suggest what this is likely to be or what the likely requirement of the kit might be. WOuld I be better to buy 12 volt TV and DVD and only use the rectifier for the laptop?