The way amperage works is that a device will demand a certain amount of power in amps, and the power supply will either be able to meet it, or not.
Think of it in truck terms. Lets say you have a 4,000lb trailer. You can tow it with a Ranger, maxing it out; or you can tow it with a F350 and have plenty of power to spare. It doesn't hurt anything to have the extra capacity, you just dont need it.
Serenity - 1999 F150 Ext Cab, Long Bed, 4.6L V8, 5 Speed, 4x4, Manual Transfercase, 3.55 Axles, Superchips Cortex Tuner, 142K miles and still going