[Sonnie]

Well... yes and no. Increasing the crossover means higher frequencies in the lower range are going to be directed to the sub. It may increase your sub response by enabling the sub to be able to play some of those lower frequencies that your mains can't play as well... but it does not extend the lowest regions of the sub bass. You got what you got there already. Increasing past 120hz may or may not help... you'll just have to experiment with it.