The stall current of your servo is 2.5A. They may be able to get away with a power supply of around 5A depending on usage, but it's not recommended. Generally speaking, you want to size your power supply and wiring for the max current that may be encountered, with some buffer. I'd recommend a 12V power supply (which are easy to find at all sorts of current ratings) with a 5V regulator to power your electronics.