Treatment might be helpful but the shape doesn't lend itself well to that, broadband absorbers need to be in the region of 6" or more in thickness to avoid them just modifying the reflections. I mean the shape of the baffle, if the driver will be inset, a small chamfered waveguide used, the width of the baffle, the native directivity of the driver being used.
These things will matter a lot, the Qtc of the cabinet will be almost irrelevant unless you make it way too high.
These things will matter a lot, the Qtc of the cabinet will be almost irrelevant unless you make it way too high.