i've had this problem too with another amp of mine. except i would get the right amt of wattage but it wouldnt go higher. like i would have the volume at 5. and it would already be blasting. and if i change it to per say 30, the bass would be the same.
but i think you should check your xovers. and your gain especially . i wouldn't use bass boost so much.
and try messing around with the EQ on the deck.
or even try checkin the deck. and voltages everywhere