Room is way too bright.

Vertical Blinds, Thick Acoustic Fabric, angled one way facing the speakers both absorb sound and block sound reaching glass/hard/reflective surface behind, and still maintain some daylight and view from other vantage points.

Heavy duty tracks, pro install for the weight, several separate sections to be individually angled/open

Consider the whole wall, above and below the windows if not full height.

What is opposite wall? Even though no windows, you could have similar to control side reflections, pull open to reveal artwork, storage, equipment on wall when not in use,

Elimination of reflections of hard side windows has been discussed. Don't mess with the content or origin, simply eliminate the problem temporarily when listening, that's the flexibility of Acoustic Fabric Vertical Blinds. Keep all that daylight, a few live plants, a living space, not a dungeon.

Toe-In combined with Tilt, directing the tweeter's output in and up to your seated ear height, will give preference to direct, essentially equal volume of primary drivers, minimizing reflections from floor, ceiling, and side walls.

Ability to adjust frequency balance at listening position to your preference is important. CD with test tones to document pre and post adjustments, 

Amazing Bytes, CD with 29 1/3 octave test tracks

and SPL mic on tripod

SPL Meter, with bottom hole for tripod mount

are needed, then use your ears, a helpful friend is always good.

Open Space behind you increases the time delay of eventual reflections. Diverse mix of angles reduces similarity of reflections to initial direct sounds.

Adjustable Toe-In for Imaging, for Single Centered or Two Off-Center Listeners

Toe-In Alternates, Stereo and Video