Dustyn, your accounting of the volume around "0" for clipping with your setup is quite helpful, thank you.
As for ohm and efficiency, short answer:
The lower the ohm rating, the higher a speaker load on power requirements, the more robust the amp needs to be. A lower ohm rating usually equates to having to buy/spend a bit more to be sure your amp is capable of driving the speaker.
The higher the efficiency, the more sound volume the speaker will produce at a lesser power level. Typically the smaller the speaker (such as bookshelves) are less efficient than larger speakers. This is why the M80s are more efficient. However the M80s also houses a fair number of drivers which is most likely why it gets its 4 ohm rating.
Again this is the short answer. Alan or others may have a more in depth description. I'm a bit short on time today, sorry.
Keep those thoughts coming though. Please report the volume for clipping on the Denon, speakers hooked up and other pertinent info.
thanks
