how much current can Samsung Galaxy S II take for charging with whatever ROM? What is the maximum power SGS2 can use when charging, given a capable charger?

I use power-consuming apps while driving a car (navigation + video registrator), and looking for ways to minimize battery drain. Ready for custom ROM if it will allow higher current.
According to this youtube video, where the user measured actual current drawn while adjusting the settings, the maximum is 650ma (.65a).

Contrary to the first answer, the charging device cannot in any way "push" current into any device; it is like the AC outlet, which can supply a lot of current, but will never supply too much unless there is a defect or short. 

The charger can only supply current, hopefully enough to satisfy the amount the device is trying to draw. You cannot damage your device by using an adaptor that supplies higher current, you can only slow down the charging by supplying too little.  The device itself contains the charging circuitry that controls how much current is drawn at various stages of charging.  

If the wall adaptor could damage a device by supplying too much current, then it would not be safe to plug it into the computer USB port, which is often capable of supplying higher current when properly negotiated by the device.