What room treatment product have transformed your room or audio system?

Been using ASC half and quarter rounds for years now along with their panels and have had great success in every room they’ve been used in but the new ASC Isotherm traps are a big leap forward in performance. Increased absorption factor, deeper reach and improved articulation. 

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.

I totally agree with Mijostyn 3 My absorbers (styrofoam) are behide the Maggies also I use defusers on side walls music is front and center stage awesome sound

ATS is great place to get affordable panels or DIY for most economical.  Knauf Ecose with FSK facing (white poly on one side) is best for taming bass and room nodes.  Not sure ATS offers the FSK version.   I found at insulation supply store.  Built frames of wood from box store, thick cardboard or 1/4 plywood backs that come 2x4'.  Fabric wrapped.   Made 6  2'x4' for about $300.  Very effective.   Corner bass traps prob better but in my modest room would be too intrusive, visually.  I didn't have a first reflection problem.