The best room upgrade: $2250


I live in hot as hell Sunny South Florida. My house is open beam ceiling (no attic). Upstairs without air conditioning on is 95* +!

I finally got around to getting the roof Siliconed to knock down the heat and UVs= lower electric bill. What I didn't know was the impact it would make, quieting my listening/TV room. For the first time in 25 years, no traffic noise from nearby I-95 and I-595!!! And when I turned on the TV the sound was relaxed, not echoing in the room. I haven't yet put the stereo on, but will later today
Glad I did this before my Voyager amp arrives- any day now. I need to get a handle on how this changes the sound before I put in the system
tweak1
Much less expensive than other treatments, try getting a dozen or two of artificial ficus trees.  5' and 8' as leafy as you can find.  I have purchased a lot of artificial ficus from At Home stores.  The 5' trees are only $40.  The 8' are more expensive, but I can't remember their price.  

They are very effective diffusers and have improved every room where I've heard them used.   
spray foam dont get that crap on your skin, acoustic treatments are great so great that I installed a Track around my room and I can have curtains all over when I want , cost me little over 1,200 the sound deadening curtains were 120 a panel and gets expensive , I picked up on amazon and there nice and heavy and do the job well and keep light out too. 
If it was spray foam insulation you used it will also extend the life of your roof shingles 
I did my attic several years ago and my attic temp went from 120+ to typically 78 degrees on a very hot day  My AC service guys love it when they have to go into my attic now, or me for that matter