Have you run REW software on your room? It’s free (although you need to buy a microphone off Amazon for cheap).
It will tell you a lot about your room and where you can spend money the most effectively.
hardest part is looking at the curve and going “”OK what now”?! But there are 10,000 smart guys on the internet (and 29,000 really stupid ones) to help figure that it.
it will save you a lot of time, money, and false starts.