TV screen behind speakers

The problem with the TV's flat surface is primary reflections, which more affect high frequencies than low.  Room modes will have more of an effect when you move the sub.

Judging from your setup, you probably cherish 2-channel listening [those Aerials are NOICE], so although moving the speakers further apart may reduce those primary high frequency reflections - you may degrade any type of staging those speakers are trying to reproduce.

What I've done occasionally during 2-channel listening is to drape a light, but airy blanket over the screen - which helps a little.  Long term plan will be to make light, but custom acoustic panels to hang on wall hooks when I eventually (someday...) hang my TV up on the wall.

When you go to First Reflection websites such as:

Locating areas of first reflections (acoustic.ua)

They indicate the center position between the speakers as a reflection point. So covering that up when listening critically is important.