Small rooms are not doomed to fail but may be more demanding of speaker/listening chair placement. I once had a similarly small room in a basement and was shocked at the quality of the sound I achieved in a near field arrangement.
Of course you will want to insulate your walls--but not for acoustic reasons. It does very little acoustically. Now double sheet rock may be worth considering. Make sure you place outlets in strategic places as you will need to see if the long or short wall sounds best. Hard to predict that. My room had a dropped ceiling--this can double as a bass trap if need be.
GIK has a good reputation. I can also recommend Audimute. Acoustic treatments are also very easy DIY projects. If you did a nearfield arrangement, I would treat the first reflection points on the sidewalls and the wall behind you with 2x4' panels to dampen reflections off those surfaces (Your seated position will probably have to be near the rear wall and you don't want all that "early reflected" sound confusing things). I would then try to work on some diffusion of the front wall or near room corners.
Just some suggestions. Have fun and good luck!