TLS Guy......To each his own. If you like the sound of your system better with the speakers set to large then great. However, it is common knowledge in the audio industry that bass reproduction sucks the most power from your amp. By setting your speakers to large, you are asking your amp to provide LF sound to all your speakers when the powered sub can do that job.......and better in most cases. It is, in my opinion a duplication of efforts.
In other words, if your speakers are capable of accurately reproducing 20-80hz frequencies then of course, you do not need a sub at all!!
As is so often true common knowledge is dead wrong!
There is little power below 80 Hz. I can assure the real power range is 80 to 2.5 KHz.
In addition the area below 80 Hz coincides with the tuning peaks of impedance and so that range stresses amps very little.
You just think a lot of power is required because subs are so inefficient.
There is the odd movie effect that takes some peak power, but bay and large there are not large power demands below 80 Hz.
If your bass system is efficient, that means large, then the power required for the sib range is not large.
In any event I have power to spare, 3.5 KW from 14 power amp channels. They all just coast.