Speakers are a complex load. Two different sets of speakers in parallel on the same amp are no more complex impedance than one speaker, although they are lower impedance, which may or may not be too low impedance for the amplifier at some frequencies and draw too much current. The impedances of two speakers in parallel do not effect each other if the amplifier is not overloaded by low impedance. The impedance curve of two speakers in parallel is not any more complex than one speaker. Impedance curves are measured with simple sine waves. Music is not a simple sine wave, so the impedance curve is a simplification.\n\nHowever, if two different speakers are wired in series, the amplifier voltage is divided between the complex impedances of the two speakers, so the impedance curve of each speaker influences the frequency response of the other speaker. The higher impedance of speakers in series is less dangerous to the amplifier than the impedance of one speaker.\n\n300W is 24.8dBW. If the speaker sensitivity is 101dB SPL at 1W at 1m, this amp with this speaker would be 126dB SPL at 300W at 1m. NIOSH Recommended Exposure Limit for 126dB SPL is 2 seconds in 24 hours. THX standard level is 85dB SPL at -20dBFS at the listening position. This amp with this speaker would be 105dB SPL at 300W at 11.7m or 38.5ft. NIOSH REL for 105dB SPL is 4 minutes 43 seconds in 24 hours. I value my hearing.\n\nThe volume control sets the voltage gain of the pre-amplifier that drives the main amplifier. The output voltage of the pre-amplifier depends on the source device output voltage and the voltage gain. The main amplifier output voltage depends on the voltage input to the amplifier and the voltage gain of the amplifier. The main amplifier output voltage and the speaker load impedance determine the output power. With music, full power of the system is probably reached well before the volume control is fully clockwise. With music, an arbitrary "three o'clock" position of the volume control would very likely overdrive the main amplifier to produce clipping, especially if it is driving low impedance with high current.\n\n\nYou can believe what you want, but what you say is erroneous. You are forgetting that resistance is scalar, but impedance is a vector, having both magnitude and direction. So your theory is a gross oversimplification of the situation.