You shouldn't really run house speakers/amps from a car sterio. Car sterio systems use a 4 ohm independance system (I think this is the resistance caused by the voice coil in the speaker, could be wrong though) and house speakers run an 8 ohm independance. The higher rating of the home equiptment will damage the sterio eventually. You can run a 12 to 240 volt power invertor in your car to run domestic appliances, but if you do this as a long term arrangement I strongly recommend you put a split charging system that you usually find in limo's or campervans and add an extra battery (preferably a leisure one) to run the 240v stuff from. It will also be worth either fitting a smaller pulley to your alternator so it spins harder creating more charge, or bette still an uprated alternator with a higher charge rate to keep up with the drain the 240v stuff will put on your 2nd battery.
In short, this ICE system wouldn't really be that lazy but is certainly do'able. I used to run a 240 volt 17" widescreen LCD TV with a 2 amp surround sound system in my limo, and with a decent charging system to keep up with the power drain it worked with no problems at all. It was very cool and very, very loud.
