the worksheets in the manuals where you have to calculate the speaker watt ratings and whatnot, where done up in a time where people didn't really understand the dynamics of an audio system. We've basically come to a new (and correct) understanding that we need to have a minimum speaker load applied to an amp to keep things from going haywire and blowing amps, and the load requirements of an amplifier are what actually determine if it can be run or not... not how may watts are attached to it.
you could in theory wire up hundreds of speakers to a single amp, provided you do it the correct way.