What about the impedence??
This is one thing that gets neglected in most discussions. The total power output as stated is 75 watts RMS. Now if this is a 5.0 system, there are more things left unsaid. Watts per channel needs to be spelled out as most rear channels are at a reduced wattage. Most likely divided as thirty watts per channel for the front and five watts for the rear pair and the center. This could be any combination that totals 75 watts. Power is voltage times current but the resistance of the speakers causes changes in the voltage as a lower resistance will give you a higher current but lower wattage. Putting speakers in parallel reduces the impedence and could cause much smoke in the amplifier final stages.