Then add Mondo's in the front corners when you can.
This will tame the rear reflections, and the Mondo's will help with bass modes in the room as well as bit more absorption of the rear-wave midbass (which is out of phase with comes off the front of the panel). This will give the system a bit more 'punch' in the critical mid-bass region.
Ditto as Gordon and Jonathan said, also, IMO, the amount of room behind speakers to wall as well as listening postion to wall behind it has an effect on the diffusion vs. absorption equation.
It would be helpful to also know your room dimensions, current distance of speakers from back and side walls, etc. A picture is worth a thousand words!