[BrianG]

For one heavy duty steering servo (~200 oz-in), 3A is more than enough. I measured current from a servo running unloaded, typically loaded, and stalled, and never got above 2.6A @ 6v IIRC. Of course, if you start using multiple servos for things like mech brakes, you might want something that has a higher current rating. But for me, these cheapies work perfectly.