Maybe it's old age, but I'm finding that when pushed a bit in our new TV room (SIM2 Mico50 and Carada 114" screen) the 803s have a bit of an edge.
The biggest challenges I have had with this hobby is when moving gear from one room to another. Ive had the exact same gear in 4 different rooms. 4 different sounds. Your new room sounds really cool. Based on the info in your post did the speakers work well in your previous room ? Without a picture we can only provide info based on assumptions and your post info. We are listening to our rooms even in a TV room.
I can't afford a full gear swap out and I've tried some interconnect and cable cable swaps with no luck.
Some speakers are more revealing of room/gear. Some are more polite sounding. No speaker is perfect. I have learned the following lessons.
a) spend some time and effort fixing the room issues if allowed (shared living space has constraints is your room shared?) if this does not resolve the problem.
b) then try different cables/interconnects.
c) finally changing gear (amps/preamps/speakers). Maybe multiple times. This is obviously what manufacturers/dealers/distributors want us to do. Maybe you want a change and have cash. IDK.
So - I would take some time with (a) first and maybe you have already your post doesnt say. In the new room I assume the new screen is between the 803 speakers? Maybe you have already done this; as an experiment have you tried covering it with a blanket and listen to see how it affects the HF? This obviously defeats the purpose of the TV room but it may tell you where the problem lies. Resolving may mean moving the speakers into the room a bit if allowed. The new room is close to being square as well which is more difficult. 800 series are very revealing of the room and the gear feeding them.