You are way too obsessed with ohms. Impedance, measured in ohms, is a property of the speaker itself, not of the amplifier. It is roughly analogous to resistance, and it varies with the frequency a speaker is playing at.
Some receivers and amplifiers have problems with lower (say, 4 ohm) resistances. Some of those (and some that don't have problems at normal settings) have a switch between 4 and 8 ohms or 4 and 6 ohms. Setting that switch to 4 ohms severely limits the power of the amplifier, which can actually damage the speaker. Therefore, you should never set the amplifier to the lower (non-normal) setting.
I have run my M80s just fine on a 75wpc receiver set to 8 ohms and now with a 140 wpc receiver set to 6 ohms.
You won't wreck the speakers unless you force the receiver into clipping by playing it at a higher level than it can handle. Fortunately, you are extremely unlikely to approach this level.
