Like others have said, I doubt you need more power. How efficient are your speakers?
If they are, for example rated at 88 DB at 1 watt/meter, that means they can produce roughly 88 DB with 1 watt input, at 1 meter (3 feet) distance.
With 94 DB efficient speakers, I use a 2-watt amp!
What happens when you just crank your receiver up? Does it start clipping harshly at some point?
Are you honestly listening to it with the volume past halfway up?
More efficient speakers will get you a larger volume increase than a bigger amp will. "If you compare the maximum volume of a 50-watt amplifier with a 100-watt amplifier the difference is only 3 dB, barely greater than the ability of the human ear to hear the difference. It would take an amplifier with 10 times more power (500 watts!) to be perceived as being twice as loud (a +10 dB increase). Keep this in mind when purchasing an amplifier or receiver. 2X the power output = +3 dB increase, 10X the power output = +10 dB increase, or twice as loud."