This room is an excellent size. See my system I am about the same size. You need treatments though but nothing really needed for near reflections of midrange/treble but you will need mostly stuff to tame the bass and mid bass - think large broadband bass traps and anything else you can get in there to absorb (plush furniture, bookshelves...etc. etc.). The modest sized space will mean that bass modes are very audible as everything will be well separated in time - unfortunately all the space will make remaining modal issues more noticeable as you have overall less masking.
