Trying to get a little more bass on the towers.
Ill start by saying, you will not get bass from a tower pod and will end up with a blown driver if you try. Mid-bass? Yes, you can get mid-bass, but its still going to be limited as how deep and how much. Both of those will depend on the size of the driver. Another factor is the tweeter type. There may be mid-bass there, but the tweeter, like an HLCD, can over power it.

A safe cross-over is going to high-pass. At what frequency will depend on what size the driver is. Amplifier wattage also plays a part in a safe cross-over. The more we turn the volume, the further that driver travels. So too much volume and too low of a bass extension = physical damage to the driver.

As to the sub woofer. In most cases, we find the biggest issue is the Fusion's default low-pass cross-over is too low. need to set it to its highest available setting.