I believe you have room to move the right speaker 6"-12" closer to the wall unit, and the same on the left. If you haven't already tried them farther apart, give it a shot and see what you think. I'd start both 12" closer to the walls (so they'll be 7.5'-8" apart), listen, move them a couple of inches closer, listen...repeat until you hear what you like...moving them back to being farther apart if necessary.
As another experiment, you can simply move your chair a foot closer to the speakers in their present position. You'll get an idea of how they'll sound moved a little farther apart in relation to your distance in the listening chair.
But, for the best results, you're better off actually moving the speakers because you'll also hear how they react to placement closer to the walls. One caveat, to mitigate standing waves don't move the left speaker so the distance from the side wall is the same as the distance from the rear wall.
Also, with the speakers farther apart, you may want to toe them in slightly.