Are you handy? I used Owens Corning 703 panels for first reflection points on sidewalls and ceiling. Wrapped them in fabric, very easy and inexpensive. Made a huge improvement in soundstage and imaging. Just be cautious while handling (mask, gloves, long sleeve shirt, etc.) and do out in the garage if you can.
Whatever you decide, just start with first reflection points and then see how you like it. It might be all you need.
Whatever you decide, just start with first reflection points and then see how you like it. It might be all you need.