I have that exact room size but with carpet over concrete. I did what @erik_squires suggested, called GIK and worked with them to treat the room properly. I ended up with 12 of their 242 panels (4 on the front and back walls and a pair per side wall) which made a significant positive change to the sound of my system. Now, I can and may go further with GIKs suggestions but at the time it worked with my budget.
My system: Anthem STR Stack> Aurum Cantus V7F & Pair of SVS 3000 micro subs