Micah, your "hunt" appears to be a bit premature. You shouldn't assume that your 4802 wouldn't be entirely satisfactory for driving the M80s and your other speakers. The M80s are slightly more sensitive than average and therefore require less power than many other speakers. Before looking to spend money on possibly unused power capacity you should try what you have first.
Speakers aren't "run" at any impedance other than what their internal wiring establishes. The impedance of typical speakers varies from about 3 ohms to 20 ohms at various frequencies and it's entirely possible that one speaker in the setup may be at the low end of the impedance range at a particular instant while another is near the top of the range. There's no such thing as a fixed impedance number and this doesn't cause any problem.
