Look at the weight of the amp, in general, the heavier the amp, the beefier the power supply, the higher the current it can provide.
Reading Spec Sheets
I often look at watts, but what about current. Is there a way to tell if an amp is high current or not. The reason why I ask is I have had amps that list more watts into 8ohms or 4 ohms, but did not sound as powerful as amps with less watts. I suspect the reason is current. So is there anything in a spec sheet that would tell current capablities.