Hey, Murph's got the claps!

I recognize that I may be wrong or in the minority on this, but I like the slave M3 idea an awful lot, especially since it would make the overall system cheaper. The second speaker would always need SOME kind of cord (either a power cord or a speaker cable). So, the only thing that the extra cost buys you is plugging it into a wall outlet instead of into the other (master) speaker.
bibere usque ad hilaritatem