I have purchased (from a certain bid site) an Apple Tv gen1 for my car (I have one at home and use it all the time with about 12,000 songs on it synced from iTunes and a great deal of them are wav files so large storage needed) (before anyone asks no I down want to compress them to make them smaller).
I have got a unit with a 640GB hard drive inside(sata) for the extra storage.
I have tonight removed the Apple internal power supply and connected it to an external 10 amp 5 volt regulator and has now been running for 4 hours no problem the heat sink on the external power regulator isn't even warm, current in amps tested at 1.05 amps to max of 1.5 amps at 12volts (suggested 7.5 amps elsewhere on the net).
I am going to leave it running all the time so i can sync it when its parked via wifi and also for quick start up time, the voltage regulator has a shut of so if the battery gets too low it will shut of leaving enough to start (hopefully, also a main kill switch for long parking).
I plan to run a wireless router in the car (12 volt regulated and ignition acc switched) with a connection to Ethernet port on the Apple Tv so I can wifi my iphone using remote Hd (also remote HD installed on Apple Tv) then when the engine is switched off and key out the Apple tv switch's to Wifi mode (tested) which then links to my home Wifi signal for syncing to itunes.
I will try and post pics up as i go