More speakers are always, always better. And why stop and two, or five, or ten, when you could have twelve of them all folded together and blasting one single channel out of an omnidirectional 3D-printed dodecahedron housing that you can make yourself for under a hundred bucks.
The reason why you might want to consider using a whole bunch of speakers instead of just a couple is that speakers, individually, only really project sound in one direction. A dodecahedron speaker, on the other hand, acts more like a point source, projecting a nearly spherical sound wave in all directions at once. This makes it great for parties and large open spaces, but if you try and buy one of these things, it'll cost you.
A better solution, if you've got the skills, is to just whip up your own omnidirectional dodec speaker using a dozen cheap 3 watt drivers plus a bunch of 3D printed parts. Don't have a 3D printer? No worries: just find your nearest hacker space, and odds are someone with some experience will be able to help you out.
What's more, the author of the project, Sean Ragan, has posted a detailed guide covering how to make one of these yourself, for as cheaply as $100.