In an acoustically-harsh room your $1500 speakers can sound no better than the $50 speakers inside your TV. Sound Absorption panels reduce reverberation and eliminate sound reflections and echoes that can muddy the sound. Commercial acoustical panels can cost $200 each or more, but these DIY specials will cost around $20 each.
Acoustical engineering weblog AcousticsFREQ offers step-by-step photos and instructions to make your own acoustical panels. You'll need dense fibreglass board insulation, materials to build a 1"x2" frame around the insulation, spray adhesive, and a sound-transparent fabric that can be found at any fabric store. Simply build a frame around the already cut-to-size insulation panels, cut your fabric to cover, and attach with spray adhesive and staples. You can then mount the panel to your wall like you would any piece of heavy artwork.
Most rooms that are tweaked for professional sound use many of these panels, but even a few should improve the acoustics in your home theatre area. I'd suggest making two of them to try behind your television as shown in the photo above and then determine if you need more to achieve your desired level of sound performance.