It might help if you tell us what speakers and gear that you have. The lack of liveliness could be due to a very warm sounding preamp/source and/or speakers rather than being inefficient. But more watts on an inefficient speaker is always good. If your have a very warm system, Bryston is probably just about the fastest responding amp I know of.
Amps that bring liveliness to low efficiency speakers?
Looking for used amps only - integrated or power amp, dual mono design. No class D!