1. Buy a nice carpet or rug for the room where you have your speakers.
2. Adding more material to the room is most often beneficial. Everything in the room
which has a textile surface like curtains and a sofa can improve sound quality.
3. The more the room is controlled acoustically the better the sound. Paintings or mirrors on the wall will reduce the effect of parallel walls and improve the stereo image.
4. A low coffee table in front of the sofa is useful to reduce the effect of floor reflections below 1-2 kHz. It’s also nice to put your feet on it when enjoying your favourite music!