The small room is definitely the main culprit. Audiofile9 also points out the speaker placement could be optimized a bit and possibly reduce the problem to some degree. In a small room, low frequencies are not supported by the room dimensions, as there is not enough space for 1/2 wavelength to travel within the room. Instead, the room is pressurized, much like what happens in a car. When rooms are pressurized in this fashion there can really be some significant problems, most revolve around pressure points in the room and then peaks of certain frequencies at certain points. I'm not speaking solely of room resonant modes here, but that no doubt is also occurring. The first thing you should do is measure the frequency response of the room using a test CD and an SPL meter. There are better ways of measuring the room, but this method is very inexpensive and will give you an idea as to what frequencies are giving you the biggest problem. Undoubtly, the room resonant modes are giving the greatest problems, but with small rooms like this you will likely find some other frequencies (or bands of frequencies) that are giving some problems as well. After you find what your current response is, you at least have a starting point. Then you can more objectively evaluate changes, such as speaker placement, listener position, and room treatment. Believe me, it's very difficult to do this solely by ear. By ear works very well for the final tweaking, but can be very frustrating in the interium because there are so many interactions occurring. For example, you may do something that compensates for one particular problem and it sounds better for some music, but then can actually sound worse for other music.