You didn't mention your room. Every flat surface in your room is a transducer that reflects, cancels and muddies the sound. How much does you sound change when you stand up? How about when you lean forward in your listening chair? Unless you have already treated your room I would suggest purchasing a couple of acoustic panels and just lean them up against wall and then move them and listen.
A simple heavy blanket over your flat screen increases clarity and depth. If you have a coffee table between you and the speakers try moving and giving it a listen. Acoustics don't have to be permanent but simple changes can make a difference and then can be removed for returning the space back to a more normal configuration. You'll also learn what make a difference and when you want to make the changes for good you'll understand it better.