Randy, first a comment on what Gene said about the gain. When a balanced connection with two wires carrying signals into the amp(instead of the one with a regular coaxial cable)is used, the two voltages combine for a 6dB increase(a voltage double is 6dB, compared to the 3dB increase for a power double). That's why, as Gene pointed out, that the gain for the balanced input is typically designed to be 6dB lower, to keep things even regardless of whether a balanced or unbalanced input is used. The Emotiva's higher gain is an interesting curiosity, but as Gene commented, it isn't of any particular significance. The gain on the unbalanced input(which you're using)is a typical number which the 2805 can surely provide enough voltage to satisfy, and even if it couldn't, the result would be distortion in the preamp, not the amp shutting down.

Yes, re-do the connections even if they look good, because those little wires can be very sneaky, and they seem to cause trouble a lot more often than the amp actually being driven too hard does. As I commented, the 6dB with doubling of distance number isn't adequate for a complete picture of power use and the dB numbers you give shouldn't cause a problem with the M80s which are "an easy 4 ohm load". I recall you mentioning when you got the M80s how your 2805 made them "sing", and it wouldn't be surprising if it still does if you connect it to the M80s to check for a shutoff(unless an internal short has developed in one of the M80s).

Despite the assurances that you've received, there may be something wrong with the Emotiva.

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Enjoy the music, not the equipment.