Square rooms are tough. Vaulted ceilings can be good--but not always. I would put your equipment in the room and take some basic frequency measurements with a test CD (we sell one) and a Radio shack SPL meter. See what the response is below 100 Hz. If you have 10 to 12 db peaks which is likely with those dimensions it's unlikely you will smooth things out without the use of a parametric eq. If your peaks are more modest then you may be able to tame them enough with appropriate trapping. If so, then you could wind up with a very comfortable listening area.
Obviously, you would need more than just bass traps--but that's going to be the biggest hurdle. If you get over that one the rest is almost certainly doable--unless you have a wall of glass or something else you haven't mentioned that could create other problems.
Obviously, you would need more than just bass traps--but that's going to be the biggest hurdle. If you get over that one the rest is almost certainly doable--unless you have a wall of glass or something else you haven't mentioned that could create other problems.