Most of the comments here are made in regard to the treatment of midrange and high frequencies. The real serious problem in a small space is in the bass frequencies, the result of room dimensions. A very good explanation and discussion of that subject by the designer of Real Traps can be found on the net. Sorry, I don’t have a link or site, but a Google search should bring it up. The interviewer is that annoying guy (he's a little "show biz", and phony sounding) with a white beard and glasses (Audioholics, I believe).
In a lot of these threads people say without the room being treated
It's a waste of money to upgrade you're system. The problem is I don't think most people know how to treat their rooms. I really think it takes a professional to know how to treat a room. Sure you can play around with it if you like but it could also be a big waste of time and money. And I know hiring a person to acoustically treat a room can't be cheap. I wonder why more people don't discuss this subject and make recommendations on who does this kind of work. When I look at the big picture this makes the most sense.