After finding the maximum speaker phone volume too low for normal use, I decided to poke around and see if there was something I could do about it. I knew that the Celestial framework folder (/System/Library/Frameworks/Celestial.framework/) had a Maximum Volume property list, so I decided to edit mine and see if I could effect a volume boost.
In the property list, I adjusted the Default -> Default value up to 0.99, up from 0.7 and found that it seemed to nicely boost my speaker volume. Is this a real fix? Or did I just psychosomatically convinced my ears that they were happier? You tell me in the comments.