Fred has pointed out the sensitivity of the array but let me add that you should plan on losing a few dB to baffle step compensation so the array will be a little less sensitive than with perfect array gain assumptions. The sensitivity stuff is in my white paper.If you read my white paper, you will find info that would help you with the crossover frequency but it suffices to say that you'll likely be in the 1000-1800 Hz range depending on the spacing of the woofers.
Let me second Fred's suggestion that you work with a person capable of designing the crossover for your line array speakers. Unless you have measuring equipment and expertise, you'll not do justice to the quality of drivers that you have.
Jim