The M3 and M80 are each rated by Axiom with a sensitivity of 88dB for 1 watt at 1 meter. Don't think that bigger speaker means bigger amplifier, because enclosure size is related to tuning for low bass extension, but has no direct relation to sensitivity and power requirements.
Oh John, I beg to differ. The sensitivity might be the same but if you take a look at the impedance graph for the M80 you would see that the speaker spends less that 10% of its frequency range above the 8Ω level. In fact the lower 1/3 of its range is averaging below the 4Ω .. That sure does suck up the amps of current and that is what the NAD3020 doesn't have much to spare. Turn it up to a listening level and you will simply cook your amp.
The M80 really does need a bit bigger unit if you don't want serious clipping.
edit -- From reading more on the NAD3020, it may be able to take it as it can work down to 72W@2Ω just don't crank the volume as I would not push it as the M80 eats current. Or that is what my amp gauges say
