To avoid replacing the existing rug, I just purchased two 2x3 rugs (super cheap!) to place in front of the speakers during listening sessions to determine whether they reduce floor bounce.
Well, "floor bounce" usually refers to cancellation around 100-300 Hz, and no rug will affect that to any degree -- carpets aren't thick enough. However, the rug will reduce HF reflections from the floor, and THAT will take some of the edge off the sound, if that's an issue. It may also improve imaging.