My current living room setup is a 3.1 channem configuration consisting of three Defintive Technologies Mythos Nine wall speakers, an SVS SB1000 12" sub, and a Marantz SR5013 receiver.
This is a great post as it is informative and you pretty much answered your own question except the main part about whether you have power "not used" or "wasted". That is your sitting distance from the speakers and when you said you wanted it "louder", what would it be in "SPL". For example:
Your receiver is capable of 100 W, 2 channel driven into 8 ohms, at 0.08% THD+N (likely performed a little better on the bench).
So if you sit 9 ft from the Mythos 9 on-walls, you should get about 105 dB peak, that is, "reference level"; and that would be about as loud as what you would hear in a movie cinema.
If you had run auto-setup, the receiver would have been calibrated to output 85 dB average, 105 dB peak with volume set to about 0, assuming your system is capable of doing it.
If you sit further than 9 ft, you will not get reference level, how much less depends a lot on your room acoustic/speaker placements but you can get a good idea using the online calculator shown above.
The speakers have an RMS power handling of 250W, and my receiver has an RMS rating of 100W per channel.
There is no such thing as RMS power, I know I cannot do anything about the common misuse of this technical term but I'd like to do my part and try anyway whenever I see opportunities. Typically speaking, the power handling specs stated as say, 20-200 W, the higher number would likely represent what they considered safe at that level during the normal/usual/typical kind of peaks in the media contents, but not the so called "RMS" (what people called, when the correct term is "average").
The rest of your long post is very interesting to read, because for just about every question you raised, you provided the correct answer yourself, as confirmed by others who responded..
I hope my "long" post help clarified things just a little more..
