I have a definite 'thing' about that bit of real estate called the front wall between the speakers - it's generally the most sensitive place for effecting speaker sound even tho there's other boundaries that might produce more significant peaks/dips like ceiling, sidewalls, etc
Unfortunately, planar speakers aren't exempt from this despite their reduced side radiation effects so your response will still be effected by what is essentially a big piece of reflective glass (well, not quite but ...) and the cabinet/stand also contributed too
So, yes, any diffusion panels behind the speakers will obviously have some direct effect on the sound in the room and, as you've possibly seen on some other setups, using some more absorber panels like you've got on the rear wall, where that big screen now rests will dampen some of the reflection peaks/dips of that front wall - I don't know how much of this is actually possible but perhaps you might ask 'bilbo' who also has some similar panels (big maggies) and is going thru some setup cures using diffusers/ absorbers - the Visoustics are pretty good value in comparison to most other pro-audio based solutions altho the people from Lithiania where I got my Schroeder foam cut diffusers also make similar ones to your photo, generally known as 'Skylines'
The advantage to buying locally is that if they 'don't work' for you, you can usually return them for refund/exchange and still benefit from their experience with the units - you do need a fairly large area for them to work well, perhaps 2 - 3 sq. metres - I would suggest you look at the 1D diffusers (like 'bilbo' had cut from foam) rather than the Skyline type from Vicoustic company behind your speakers - the best benefits of the Skylines (Vicoustic ones) is on the ceilings, would you believe - not sure how you 'make them invisible' there as youcan't put a cloth cover in front of that irregular surface, - very effective for 'ordinary, non-planar' speakers but not sure how they'd effect the sound with those speakers of yours
There's a mob down here that's developed a newer type of absorber panel that's worth a good look - they add a piece of clear Perspex in front of the foam panel - 'the "Sound Acoustic" company, and they offer 8 pieces of 600mm x 600mm for $440 that's a pretty good offer - you can also get these cut from a similar type of acoustic foam and use a nicely finished 'plywood' instead of the clear Perspex for a more aesthetic finish - his name is also 'James' so he must be a good guy!!
I'll try to add some photos from their site - quite instructive, particularly if you're thinking about more diy projects - there's a variation of the familiar 'bass traps' that caught my eye - it's a bit chunkie about 7" thick but colours are mentioned and using a plywood insert panel makes them more acceptable for a lounge room
Don't seem to be able to add the photos but look at their 'Sound acoustic' site - the bass traps are HAB600/150 and diffusers are HA600-75 Hybrid Acoustic Absorber/Diffuser - I should ask for a commission, eh!