Looking at your drawing, I would definitely agree with Shadorne that the TV is not the main issue. In fact, I would say that the sliding glass door behind the left speaker, and the entryway behind the right speaker probably have even more to do with the loss in your soundstage depth than the TV in-between the speakers does. But the main thing is that they should ideally be on one of the short walls.
My brother has a similar situation to yours, and also has a large TV between his speakers. He experimented with removing the TV (and also covering it as you did) and found it made no significant difference to the overall soundstage, so he put it back. He unfortunately cannot place his speakers on the short wall. If you can, this is by far the best solution. If not, I would also consider curtaining the screen door somehow, and if there is not a door on that entryway, considering putting something there as well.
I myself have a large plasma TV between my speakers (as well as my audio rack, for that matter), but they are on a short wall and the speakers are also horns, so their shape minimizes the effects of the room anyway by directing the sound much more where I want it to go, even though the set-up is very far from a theoretical ideal. I also have plenty of diffusion throughout the room, which is also much larger, so I have plenty of space behind the listening spot. The effect of the TV is therefore very minor in my set-up. I have a huge soundstage however you want to measure it - width, depth or height. I am sure it could be improved by better placement, but that is not possible with the other furniture in the room. I hope someday to have a dedicated room, but that is years off yet.
My brother has a similar situation to yours, and also has a large TV between his speakers. He experimented with removing the TV (and also covering it as you did) and found it made no significant difference to the overall soundstage, so he put it back. He unfortunately cannot place his speakers on the short wall. If you can, this is by far the best solution. If not, I would also consider curtaining the screen door somehow, and if there is not a door on that entryway, considering putting something there as well.
I myself have a large plasma TV between my speakers (as well as my audio rack, for that matter), but they are on a short wall and the speakers are also horns, so their shape minimizes the effects of the room anyway by directing the sound much more where I want it to go, even though the set-up is very far from a theoretical ideal. I also have plenty of diffusion throughout the room, which is also much larger, so I have plenty of space behind the listening spot. The effect of the TV is therefore very minor in my set-up. I have a huge soundstage however you want to measure it - width, depth or height. I am sure it could be improved by better placement, but that is not possible with the other furniture in the room. I hope someday to have a dedicated room, but that is years off yet.