The simple and easy solution is to get a Mexican blanket, or a small art quilt or any padded thing and throw it over the TV to cut back on the high frequency reflections. The more bulk you can put over it the better, since it will reflect less of the waveform if it is thicker rather than thinner. Also move is back a bit behind the front plane of the speakers.
How about one of the new style art panels on a moveable stand placed in front of the TV? Or maybe even a diffuser panel (not sire about this one, but I'm sure the experts will chime in).
Bob