Troy, the IHF dynamic power rating is one in which a 20 millisecond(thousandths of a second)sound burst is applied at half-second intervals and the maximum output capability for the 20 milliseconds is measured. This might seem to be a uselessly short period, but it's of some significance in that the beginning of a sound transient is its highest level and may be at that level for only about that length of time. Note that the 2 ohm dynamic power rating, which many manufacturers quote, in no way is meant to imply that a 2 ohm load could be driven except for that brief period. You may be making this power thing a lot more complicated than necessary, worrying over very small differences of no more than a few tens of watts. The Denon, along with the others you've considered, should be very satisfactory with the M80s in most setups. I've seen it tested at around 180 watts into 4ohms and 250 watts 4ohm IHF dynamic power.
