Bright room, help

Owens Corning 703 fiber board covered in fabric. You can make it look nice (any fabric you pick). You only have to use flame retardant like Guilford if it is permanently mounted to the walls. You may choose the Guilford anyway, but it is a little more expensive. This is a great absorber, broad band, and relatively inexpensive. Be sure to use it at the first reflection points and then you can experiment. Behind the listener often needs diffusion and/or absorbtion.

You can hang rug on the wall behind where the speakers stand.
Also placing a rug on the floor where the rig stands will be also as helpful.

place a rug between the speakers and your listening position to eliminate floor reflections of the uppermids and high frequencies. adjust toe in to avoid side wall reflections or add deadening materiel on the side wall reflection points, including book cases, plants etc. don't be afraid to put the speaker axis's crossed in front of the listening position. adjust speaker heighth. you might list your equipment as some may be able to comment on ways to tame the equipment itself.