If you have direct access to your pre-amps outputs, you would ideally connect your pre-amp outputs to the minidsp inputs. You would then connect two of the minidsp outputs to your main amp and the other two outputs to the Dayton amps using a “Y” cable. Assuming you need to use both left and right inputs on the Dayton amps.
Another option would be to use a DBX PA2 instead of the minidsp and connect your pre-amp outputs to the DBX inputs, then connect two of the DBX outputs to your main amp, two of the outputs to the left Dayton and the last two outputs to the right Dayton.
A third option would be to connect the pre-amp outputs with “Y” cables to the Daytons inputs and then connects the the Daytons high pass outputs back to your main amp’s inputs.
All of these connections assume you have pre outputs and inputs of some type.