Once again - it doesn't really matter how many channels are driven - there are almost no all-channels-used at max level scenes in any movie. Even fewer sustained for more than instantaneous peaks...and the small difference in the actual wattage won't contribute to performance gains of any substance, anyway.
If all-channels-driven specs are worrying you, you really need much more power than a receiver offers.
Wouldn't worry about this non-issue. It's something fan-boys created to try to one-up other fan-boys.