Yes, nominal impedance in series connection will double.
However maggies typically are an "easy" 4 ohms, meaning mostly resistive load so many amplifiers will be able to drive them without a problem. Sensitivity is quite low (~8x dB/W) so better have some power headroom in amplifier.
Biggest issue in your planned configuration is how to place two speakers /channel. Only valid way would be to make extra high line source by placing one on top of another, IMHO.
Yet again, YMMV.