Hi Blixten,
Love the equipment and attention to room acoustics - you're like in that regard. If you listen from the leather(?) couch against the back wall, may I suggest you place thick absorption there instead of the 2D diffusers? Sitting so close to diffusers isn't normally advised so say Prof Cox diffusion expert. Perahps you've already tried absorption there; in any event it'd be interesting to hear your impressions on both approaches. Cheers, kevin