Many bookshelf speakers are accurate and will play as loudly as one would possibly need, with low distortion, especially when they have the bass frequencies filtered away from them. The only generalization you can make about larger, floor standing, full range speakers is that they have more bass extension into lower octaves that bookshelf speakers can't do with the same general efficiency.
Tony Hoffman, physicist, first at AR and then later KLH (he was the "H") came up with the guiding mathematical principal, generally called "Hoffman's Iron Law
" which applies directly to acoustic suspension designs AR (and later KLH) were famous for, quite precisely, however it sort of applies to bass reflex (ducts/ports, and passive radiators) designs too, at least roughly. It states: "Deep bass extension, high efficiency, and small cabinet size: Pick any two
." A bookshelf speaker picks the last two and sacrifices the first one, bass extension, but it doesn't need
that if it has the help of a sub.Edited by m. zillch - 6/26/12 at 11:57pm