That's a good sized room; have you tried clapping your hands in the center of the room to hear how "live" it sounds? Does the bass sound tight or is it boomy? You may find that you need some absorption or diffusion panels.
It's good that you've got the speakers away from the walls, but 2 vertical absorption panels behind the spkrs and 2 on side walls would benefit, just as Ghosthouse has suggested.
It's good that you've got the speakers away from the walls, but 2 vertical absorption panels behind the spkrs and 2 on side walls would benefit, just as Ghosthouse has suggested.