The space between the speakers

A friend with this set up uses a echobusters panel hung horizontally from the corner of the TV when listening to two channel. Reflections are greatly attentuated.

Here is a good example of what to do: Eric's System In this case the speakers are slightly in front of the edges of the screen - this means there is no edge diffraction from a sharp edge, as the TV vertical edges are in the acoustic shadow of the speaker.

Essentially, all the comments above are accurate. Ideally you want nothing between the speakers but real life means most of us don't have room for a dedicated audio shrine. As suggested above, if at all possible, ensure that the speakers are at least several inches in front of the TV; this should minimize most issues if you use a blanket over the TV. Essentially, with a setup like that the only thing that you will be compromising on is depth of the center of the soundstage (it will still be deep but it won't be as deep as it will be to the sides).

I think your setup overall will be fine although you may have to treat the room but that is often the case for any setup.

I have the exact same setup as you have and I have achieved a great sound. Go for it and work with it...too often we expect to plop great gear in a room (any room) and get great results. With care and system matching you should be able to achieve more than satisfying sound.

don't waste your money if this is what your setup must be....I'd go monitor speakers on stands with a dedicated sub....but still you have to get the driver faces beyond that large cabinet as much as possible.