Might ~ technically work, but then the trip through the amp and the trip through the preamp would take different amounts of time and the sound wouldn't line up ... in reality only a crossover with subwoofer out will provide the "best" results. The sound will come out of the Presonus speakers, and sometime after that the sound would come out of the subs... might only be a few milliseconds (might be more) but the ear can hear timing differential of around 2 milliseconds.