You have what they used to call a bright system. Brightness is elevated by hard walls. Glass and brick. Some wire also leads to more high frequency output. Interesting you find the streaming worse than cd or lp. That tells you your streamer is bright. What do you have for a cd player? Turntable? Cartridge? Personally I like walls treated with refraction and only a wee bit of absorbsion. A thin curtain a sheer on the wall behind the speakers will help. Just for a try grab some bath towels and tape them on the walls at the first reflection points. Find those with a mirror. Sit in you chair have someone else hold a mirror along the wall and move back and forth till you can see the center of the speaker. Hand the towel up at that point. The second reflection point is where you can see the opposite side speaker hang another towel there. Listen and see what you think. Then if you like that the quest becomes finding the right material that is even better and looks decent. Before you spend anything you cam try it and see what you think.
Regards.