Pain, welcome. If by a "straight" answer you mean one that would apply in all possible circumstances, nobody can give you that. It isn't simply a case of a given amp and a given speaker; the distance of the listener, the size of the room, the dynamic range of the music being played, and the average sound level someone chooses to listen at are some of the variables. The 2500 isn't a "6-8" ohm receiver except in the owners manual(the common warning due primarily to legal liability questions). In the real world it puts out well over 100 watts per channel into 4 ohms. Keep in mind that at a comfortably loud average level speakers such as the M60 and M80 will be using about 1 watt,while brief split-second peaks might use 100 watts or more, depending on the factors mentioned above. In my view the 2500/M80 combination would be fine in most circumstances, but "most" may or may not include your circumstances.
