Soundbar

It seems like a soundbar is the most popular solution at my friends' homes.

Soundbar brings a set of speakers placed in a rather wide enclosure that can fit nicely under your TV. I totally agree it might be easiest way to improve the sound of any “flat screen”.

There are much more complex products, some companies would call them “sound projectors” that include an array of rather directional drivers targeting different places of the room to make you feel that you are indeed surrouned by sonud.

I like the family of those products, especially due to the fact they behave like an AVR and they can:

accept multiple HDMI sources
decode a variety types of sound (including DTS, DTS-X)

💡

You can expect that with a sound projector your audio system will sound nicer than with a regular soundbar, but it cannot replace a setup with separated speakers placed in different places of your room.