i had at one time thought of making a small box that would house the amp and power supply. this box would attach to the back of a speaker, over the speaker terminals, thus not altering the volume of the speaker, and allowing it to be free to "breathe".
if you had an enclosure that was slim enough, it wouldnt change the overall depth of the speaker much at all.
or, if you wanna be super cool, build speaker stands with amps built in. a power cord comes out the bottom and little pig-tail leads come out at the top and connect to the speaker. you would have plenty of real estate to build whatever inside the stand, not to mention sufficient cooling.