Sound bar in a box . . . can't understand dialog.

I had a very similar situation. Put my main system in the family room, but in the living room we had a three-wide Salamander cabinet with a shelf going all the way across that had housed a sound bar (Def Tech) in our old house. In the new set up I crammed into this space Def Tech monitors and a center channel speaker.  Only the subwoofer outside the cabinet.  Better equipment than the sound bar, but dialog uniteligible.  First of all it was the room. Old house had a small room and the sound bar worked fine. New house has cathedral ceiling, large room, lot of glass. What I did to fix it was to get sound absorbing foam from parts express, with an adhesive on one side , and put it on the sides, tops and backs of the cabinet shelf. Then fluff designed for inside speaker cabinets (loosely) in the remaining space.  Put the speakers on rubber cones/feet.  This helped enormously.  Still, I find the sound much better directly in front of the cabinet.  Not perfect, but no room for floor stands, wife’s happy, and it’s not my main system anyway.

I sorted out my mother's TV sound with a cheapo Logitech 2.1 computer speaker set. The sub has its own volume control, which makes balancing the sound fairly straightforward.

Personally, I put the TV through my hi-fi, and am very pleased with the results.

I did something similar, threw together a patchwork of left over mini-monitors with an old Kyocera receiver.  The monitors are attached to the doors so they swing out of the credenza cavity and don't excite the volume like the soundbar did.  

or get a panasonic oled tv,,, the whole tv itself it the  speaker panel.
works great and wife friendly.