Assuming you can set a high pass filter, set it high, not low. :) 80 Hz to 120 Hz is a good point. Lower than this won't be useful.
If your main speakers are ported I strongly recommend you seal them. This will give you additional headroom and make it easier to integrate.
If your main speakers are ported I strongly recommend you seal them. This will give you additional headroom and make it easier to integrate.