most people don't need extra amp power but some people need all they can get. for example, my speakers are 5 driver 6 ohm nominal 4 ohm mininum speakers that are rated at 83db sensitivity, running them with a receiver was ok at low volumes, but at medium volumes it was a joke. I wasn't happy until i bought an amp for each one and biamped them ,then they came alive, and they are only receiving half of their recommeneded continuous watts rms. If they were 90db, i don't think i would of needed to upgrade.