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
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
To clarify, the silicone is applied on top the roof
Where I used to turn my volume in the low 60s, I can hear quite a bit at < 40
OMG, the house is so much cooler, which was the point all along
If you want to investigate I got 2 estimates, the one I chose was $2250, the other $7,000! And the $2550 job was very professionally done
OP and others, thanks for all the useful and interesting information. Incidentally, we are in the process of getting our roof deck foamed for better energy efficiency in our hot, Phoenix summers. Never thought that better sound would be icing on the cake. Now I'm even more motivated.
For those that don't want the expense of a spray foam attic or silicone application, you can add an attic fan The one l have is controlled by my smart phone  It lowers my attic temp from the 120's to high 80's but there is the additional electrical cost to consider