My understanding is that as long as the power adapter meets the voltage and minimum amperage, any higher amperage is fine for the computer. Using a power adapter with too high voltage will damage the electronics, but the electronics will only use as much amperage it needs.

Of course, in some circumstances, using a power adapter that does not supply enough voltage/current could be damaging because the electronics will demand more power than the adapter can supply. The exception are devices designed to work with varying voltages (ie AA alkaline batteries).