To double the perceived volume you need 10x the power.
However, not all speakers have equal efficiencies, and you may not want it louder but you want more bass. Depends on what exactly you want to accomplish.
You may be better off looking for speakers with higher rated sensitivities than you currently have, or to add a subwoofer.
Also, if you are turning it up for detail that's often a sign your room is too reflective.