The current depends on the load. I don't know if that amplifier will ever "draw" 10A. It will draw more current a higher power and with lower impedance speakers. In other words, you can ignore the power supply's current rating as long as it can supply the required current when needed. i.e. The battery in your car can supply hundreds of amps but car stereo is only using a couple of amps (unless you have a "killer" sound system.

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There may be a difference with different voltages at idle, or there may not be.
Under normal operating conditions I wouldn't expect much difference UNLESS you "take advantage" of the additional voltage by turning-up the volume for more wattage into your speakers.
Some basic electronic math:
Current (Amps) = Voltage / Resistance. That's Ohm's Law. It defines the relationship between voltage, resistance, and current and it's the 1st thing you lean when you study electronics.. We don't know the effective resistance of the amplifier, and we usually don't care, and it depends on the conditions. The more power the amplifier is putting-out, the more current it draws so that means lower resistance. You could calculate the effective resistance at idle if you know (or measure) the voltage and you measure the current... But the real question is usually the current anyway.
Power (wattage) = Voltage x Current. When you turn-up the volume, more voltage goes to the speakers and the speakers draw proportionally more current,
From Ohms Law, you can derive
Power = Voltage Squared/Resistance. or Voltage Squared / Impedance. As you may know, impedance is also Ohms but unlike pure resistance it can be different at different frequencies.
With a single-ended supply and a "normal" single-ended amplifier, the power supply limits the maximum peak-to-peak voltage. RMS voltage (which determines the power with AC) is about 0.354 times peak-to-peak. So about 17V RMS from a 48V power supply. That's a theoretical maximum of 72W ingo 4-Ohms (unrealistically) assuming no voltage-loss through the amplifier. With a bridge amplifier you can get double the peak-to-peak and RMS voltage for 4 times the power.