I had a Yamaha until recently and, although you could technically set it to BOTH and SMALL, the manual states that the crossover will be used (sub will get the bass). However, it did not say if you would end up with more bass (3db) because of channel doubling or not. But, to go back to the topic at hand, the bass under 90hz (my old receiver's hard-coded crossover) will go to the sub.

See Mojo's signature