I think here the room really is the elephant in the room. 20 sq m is small, and too small for great dynamics or deep bass. That is just physics. Depending on the precise dimensions, the Schroeder frequency will be somewhere in the range 175-200 Hz. Below that, there is trouble. Put some full range speakers in a room like that, and you will regret it: you will suffer bad room modes at quite high frequencies compared to bigger rooms, and their upper harmonics as well.
So I was thinking that perhaps you should start bottom up: how can I get quite extended but very clean bass? Only when you have sorted that can you move to mid range etc. As others have said, bass traps may help, but in a small room there is little space for them (and perhaps even less tolerance). So you have two options. The first is to avoid much deep bass altogether, using mini monitors like the Harbeth P3ESR. Perhaps you could move up one size with something like the Harbeth M 30.1 that I suggested earlier, but that is about it. But there is an alternative, and it is to use multiple small subwoofers, at least two but for the best result four. See here for some introduction to the relevant research: http://www.acousticfrontiers.com/20101029using-multiple-subwoofers-to-improve-bass-the-welti-devanti...
By themselves mutiple subs already give a much smoother result, but if you then add dsp room eq the benefits will be available over a much larger listening area.
After that, and I think only after that, is it time to think about the main speakers. Avoid getting big ones for that. If money is not tight, the forthcoming DSpeaker X4 pre amplifier/DAC/room eq may be interesting as it gives you the opportunity to also equalize the bottom end of the main speakers. But realize that the higher the frequency that you equalize, the smaller the equalized listening position.
So I was thinking that perhaps you should start bottom up: how can I get quite extended but very clean bass? Only when you have sorted that can you move to mid range etc. As others have said, bass traps may help, but in a small room there is little space for them (and perhaps even less tolerance). So you have two options. The first is to avoid much deep bass altogether, using mini monitors like the Harbeth P3ESR. Perhaps you could move up one size with something like the Harbeth M 30.1 that I suggested earlier, but that is about it. But there is an alternative, and it is to use multiple small subwoofers, at least two but for the best result four. See here for some introduction to the relevant research: http://www.acousticfrontiers.com/20101029using-multiple-subwoofers-to-improve-bass-the-welti-devanti...
By themselves mutiple subs already give a much smoother result, but if you then add dsp room eq the benefits will be available over a much larger listening area.
After that, and I think only after that, is it time to think about the main speakers. Avoid getting big ones for that. If money is not tight, the forthcoming DSpeaker X4 pre amplifier/DAC/room eq may be interesting as it gives you the opportunity to also equalize the bottom end of the main speakers. But realize that the higher the frequency that you equalize, the smaller the equalized listening position.
