No echo might be good for a studio where you can make the sound wet electronically. But a home theater needs some life to it. Seach the internet for acoustical treatment. You wll find that it's customary to completely deaden the first reflection points. The first reflection points are those areas that the sound hits and bounces ONE time before reaching your ears. Think three dimensionally and you will discover spots on the left and right walls, the floor, the ceiling and, one that is usually missed, the back wall. Some suggest a small mirror be moved around and where someone in the seating area can see the speakers, that is a first reflection point. That takes two people and a lot of patience, but gives you an idea of where to look. The first reflection points are the first areas to treat - make sure it's a broadband absorber - because the sound coming from them is very close time-wise to the direct sound from the speakers and muddles the sound and confuses the brain. Beyond those first points, a certain amount of absorption AND diffusion. It gets complicated. Google and read everything you can find. Eventually, it will start to make sense and you can formulate a plan.
BTW, carpet is NOT a broadband absorber.
Follw the link in my sig and see how I treated my walls. ONly my front cavity is "finished" while the other spots have only carpet - so far.