A more powerful amp tends to offer advantages at both low and higher volumes. You may have noticed with some amp/speaker combinations when you turn up the volume the overall sound improves -more open, detailed etc. With a more powerful amp, even at low volumes things open up and are more detailed - equal to playing at higher volumes.
The other issue is some speakers (like mine) are power pigs - 84db, 3/4 ohm load. While you can get sound out of them with a low powered amp (I even got them working with a 13wpc fatman tube amp), the sound is dull with no dynamics. More power fixes that at all volumes.
The other issue is some speakers (like mine) are power pigs - 84db, 3/4 ohm load. While you can get sound out of them with a low powered amp (I even got them working with a 13wpc fatman tube amp), the sound is dull with no dynamics. More power fixes that at all volumes.