Suddenly it occurs to me: is there any source out there that drives all seven channels loud? At the same time?

This power rating, noted by somebody to be two channels driven, is a little weird, too. If you are plahing surround, and two channels are driven, then you have sound in, what, your center and front left? That sounds like a measurement in stereo. And the 110 x 7 is saying that if you can put in enough voltage, you will get out 110 watts (but then they fudge by not pointing out that it is not the nature of 5.1 or any other format to have equal level signals all around, so their number is meaningless).

As for the issue of gain, and how hard one is pushing the amp, well, when you adjust the volume control, you do not adjust the gain. Amps are built with set amounts of gain, and the volume control attenuates the signal going into the amp in order to lower the level coming out of the amp.

And if your signal level going into the volume control is low, then the control will have to be turned higher to get more output. Depending on the input level, full volume might give you ten watts!

I have found many digital sources with levels that do not match other sources. Typically the digitals will be lower in volume for a given volume setting, but occasionally higher. To prove how much your receiver can put out, feed it an FM antenna signal and see how loud your speakers will play. The receiver is designed to be able to play at full volume from its tuner's audio signal.

THEN if you do not have enough volume with digital, you will know it is not for lack of power amp, but lack of signal voltage before the power amp.