Diffusion or Absorption

I'm completing the construction of my home media room (and home theater). Would like some thoughts on dealing with the solid core steel doors. I have a single door midway back on the right hand side, entrance from the rest of the house. And, I have a double solid core steel door in the back left of the room, outside entrance and exit. I originally was going to treat them for absorption, but now I'm thinking perhaps diffusion is the way to go.

Few other pertinent facts. Room measures 14 x 24 with 9 foot ceilings. The walls are double sheetrock with Green-glue hung on metal hat channel. I have GIK acoustic bass traps and diffusers in the back corners. In the front corners I have basic foam absorption and a heavy drape that covers the entire wall....Thanks