An amp will sound more powerful if it can double it's output into a 4ohm load or triple into a 2 ohm load.For instance the spec. sheet may read:40 watts into 8 ohms,80 watts into 4ohms,120 watts into 2 ohms.Many spec. sheets don't include that info. but a call or email to the manufacturer will provide you with that spec.
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.