After everything that has been posted (thanks to all) I think we can all agree...
WE NEED MORE POWER!
I distinctly disagree.
although it should have been obvious that running any electronic component at 100% could cause a malfunction [that combined load and power use would have seriously if not critically taxed the PSU of any receiver] why not look at the other factors affecting the 'problem' such as distance rather than trying to compensate with power?
you have to remember that in adding more power, speakers will come to their physical excursion limits which still may not produce the sound pressure levels that you would like to have 60 ft. away from your stereo system.
possibly what you need are either much larger speakers like those designed for rock concerts, or move closer to your stereo!
along that same line of thinking, move part of the system closer to you.
I don't understand why you have to be 60 ft. away to listen to sound pressure levels from four speakers when you can move half of them closer. Take your second set of speakers, move them closer, and only run one pair at a time off of the receiver depending on where you are in the room.
I have to agree with the limited comments here made about listening levels. the sound pressure level from four speakers playing that loudly can severely damage one's hearing