On several occasions I have laminated the back of cabinets with P-lam. The intention has been to clean up the typically unfinished backs of beat cabinets. The unintended consequence has been tighter bass response due to the stiffer back. After the first one (Marantz Imperial 6g's) I have since done the same to AudioAnalyst M8's and another pair that I am drawing a blank on. Currently thinking of doing same to a pair of ADS L620's.
I know that's a little different than what you proposed. But, your query made me think of this. Even with front to back bracing the back is still usually the largest unsupported surface. I suppose that a laminate back is more reflective than painted MDF or particle board. However, I have only had positive results.