Room is way too bright.

Maybe you have wall between windows and can make "shutters" out of panels and flip them over the glass during a session and flip them back to look like deco when not listening seriously. At least at the first reflection spots.

Treat the room as much as the budget and WAF will allow.  Stay away from any synthetic fabrics/rugs.  Natural fibers will do what you're looking for.  If room allows, experiment with some tall natural plants, you would be surprised what this will do, especially at the first point of reflection.

Thanks to all for your suggestions,

I keep hearing about this"first point of reflection."

What exactly is that? I read about running a mirror along the wall and looking for a speaker.

Check it out,

https://www.gikacoustics.com/treating-first-reflections/

Reflection points represent the primary locations in a room where sound waves first reflect off surfaces before reaching the listener's ears. 

Not just eq. DSP! Room correction using DSP even better. Problem solved.