It's not right, they should be set to small too. Large and small means how much frequency the speakers are able to play. Large would be full range speakers, where as small means they lack the ability to play the lower frequencies, as it's the case with bose ones.
My recommended settings: All speakers to small and the subwoofer crossover to 140 or so. Unfortunately, the bose cubes are so damn small that they can't even play the upper bass. I'd say that, under 120Hz, they have nothing at all, so cross the sub at 140 and check how it sounds.