That's really a loaded question.
Conventional wisdom says get a bigger amp. A bigger amp(s) will definitely sound louder but will it sound "clean" given the room acoustics?
The room acoustics contribute greatly to the perception of spaciousness, image broadening and echo. If the room is critically damped (walls and ceiling that are highly sound absorbant), then adding amplification will increase the sound pressure and preserve sound "cleanliness". If on the other hand the room surfaces are highly reflective, adding more power could lead to echos and utter destruction of sound quality.
These characteristics are also a function of direct and reflected sound path distances in the room. An acoustic path study would definitely reveal all of the influences.
I have a very live room and I achieve nominal levels of 85dB with less than a half watt nominal into each M80. The sound is clean and spacious. But if I turn it up too much, it starts to sound garbled particularly with rock music due to lengthy reflection delays. I find that by using DPLII and turning down my M80s and VP150 by 5dB, I can get it loud and simulate a deep sound stage without muddying up the sound.
