Nick, although I've commented on the interesting(to me, at least)technical aspects of drivers connected in series, I should also reply to your basic question. I tend to agree with Cork, and you may be over-thinking this shaker setup. Wiring four in series for each row and using that Sherwood receiver(theoretically about 50 watts per channel into 16 ohms, which is also just a theoretical number)would be relatively simple and should be plenty to get the folks all shook up.
Any concerns about frequency fluctuations would be minimal with identical drivers with identical impedance graphs. Also, any possible irregularities caused by series connection would be less bothersome in shaking as compared to listening, although ardent "audiophiles" might claim that their butts were just as golden as their ears.
